Let's start off by making one thing clear: Transitioning looks different for everyone. Transitions can include any combination of the following, ranging all the way from all/several of them to just one/a few:
Non medical transitioning
- Voice therapy
- Name change
- Change of pronouns
- Changing the legal gender marker (The one on your ID. Do note that in many countries, we are still not allowed to do this without having gone through some amount of medical transition. Which kinds of medical transition is required varies. Many countries also require a "real life experience", where you live with your transition results for a period of time - usually months to years - before they allow gender marker change)
- Clothing, hairstyle, other non permanent visual changes
- Mannerisms
I'll place this inbetween the categories, as it is technically permanent but not as invasive as most of the options under medical transition: Laser hair removal. Many trans women use this to eradicate unwanted facial and body hair.
Medical transition
- Hormone replacement therapy (estrogen for trans women, testosterone for trans men, hormone stoppers for young people awaiting evaluation. Nonbinary people may also go through hormone therapy)
- Chest surgery. Implants for trans women, mastectomy or other chest flattening procedures for trans men. Nonbinary people may also get chest surgery of any type.
- Facial surgery. Some trans women get feminizing facial surgery, some trans men get masculinizing facial surgery (although this is more rare since testosterone often masculinizes the face enough to satisfy the individual). Some trans men get a hair transplant to form a beard, if they are not satisfied with the beard they get from testosterone or if they don't go on testosterone at all but want a beard.
- Vocal chord surgery. Very rare but some trans women "shave" their vocal cords to make them thinner, thus giving them a higher pitched voice. Like all surgeries it comes with many risks and complications, one of the risks being practical loss of the voice.
- Genital surgery. This is what people often talk about when they say "the surgery" about trans surgeries. We are often asked if we have had "the surgery" yet. In reality, "the surgery" doesn't exist. There are many different types of surgeries a trans person can opt for (as you may know now by this list), and even within the area of genital surgery there are many different options for either gender!
- Other surgeries. Like all people, trans people can have insecurities with their body. Some trans women undergo surgeries to get broader hips/a bigger butt, some trans men liposuction their hips or butt, and there are many other procedures a trans person can undergo to alleviate dysphoria that most people wouldn't even think of!
Sometimes the transition forms a person chooses are because of dysphoria, sometimes we may undergo procedures just to obtain a more functional life. For example a trans man who isn't all that bothered by his chest may still choose to get surgery in order to be able to swim and bathe in public with his friends like any other guy. Sure, it would be great to live in a society where he wouldn't need to do that, but society isn't there yet and he should neither have to wait nor suffer until it is!
With all of this out of the way, I'll adress your specific questions.
This depends. I will assume here that in this scenario, you're talking about a trans woman who is on estrogen.
Hormones only: The reproductive organs usually don't produce functional reproductive materia anymore during hormone therapy. It does vary a lot, however, and even on hormones it is still recommended to use protection if one wishes to avoid pregnancy (in case the trans woman is sexually active with someone who has ovaries. Of course whether protection is needed or not also depends on the type of sexual activity they engage in).
She is not permanently sterile though! If she quits her hormone therapy, most of the time she can produce reproductive materia again.
If she has had bottom surgery: A competent doctor will always recommend and give the option for a trans person to extract and save some reproductive materia before any hormonal or genital transition is initiated, so even if she became sterile due to either of them she could still have a biological baby.
??? This is one I have never heard of. Where did you hear this?
I can actually neither confirm nor reject this one, but I will say I know several trans women and have never heard of this issue so if there is a difference it's probably not that big. I would love it if someone who knows the answer to this could educate me.
A trans woman who goes on estrogen will not get more facial hair and chest hair than they already have, and in many cases it will lessen a little. In practice this means it all depends on when she starts on estrogen.
If she starts on estrogen before puberty she will most likely not get any chest hair or facial hair at all.
If she starts on estrogen after/late during puberty she may already have gotten facial hair and body hair. If she has, it will lessen but usually not disappear. Luckily, laser hair removal can still help her if she wishes to get rid of it!
Armpit hair is pretty much the same for either gender tbh.
This depends a lot on the individual... There are trans women out there who pretty much had boobs already before hormone replacement therapy, just like there are trans men who never have chest surgery and are still perceived as flat chested. You would be surprised to know how different bodies can be!
A trans woman's boobs will not automatically look more like man boobs as far as I know. The shape of someone's breasts will differ a lot from one person to another, this is true for cis women and trans women alike.
How her breasts change on estrogen depends on genetics. Trans women are often told to expect to get 1-2 cup sizes smaller than their cis female family members. This expectation may have changed in recent years with new data being available, but last time I checked this was still something doctors told transgender patients... I would imagine the shape of her breasts depends on those same genetics.
Genetics play into pretty much everything here. Her hips and her other changes depend on genetics. Same goes for transmen. It is a common misunderstanding that trans men will not get all that deep voices, but in reality they get pretty much the same depth as their cis male family members.
There are of course exceptions!
Breast cancer being a risk of hormone therapy is a fear that has been prevalent in the medical community surrounding trans people for many years. Most licensed doctors don't consider this factual anymore though. There is no reliable data that proves the risk of breast cancer to be higher in transgender people who go on hormones than in the general population.
First off, please do not refer to her genitalia as a "dick". Some trans women do that, but most do not. As a cis person writing a trans character, the wisest approach for you to take would be to call it "genitals" or any female coded genital word.
If a trans woman chooses to use words that have traditionally been considered male coded to describe her genitalia, she has every right to do that. But only she has that right, and she only has the right to decide that for her own body - she does not have the right to decide what to call other trans women's genitalia.
I understand you probably just used "dick" here for lack of a better word and to be specific, but I figured I would point this out to you since you are making an effort to do respectful writing and it would be good for you to know!
With that out of the way, a trans woman who goes on hormones after puberty often sees some shrinkage in the genital region.
A trans woman who goes on hormones before puberty will not see any growth in the genital region to begin with. The potential downside to this is that if she wishes to have genital surgery, her genitals will not be able to create a very deep vagina. For some trans women this does not matter, and there are also other ways to form a deep vagina if it does matter to her. In practice, the pros of early hormonal transition often outweigh the cons for most trans women.
I have no specific data on this since early transitioned trans women are not so common yet, but in most cases an early transition will mean it is harder to differentiate the trans person from a cis person of the same gender in the same family. So it is pretty likely that her chest size will be similar to that of her cis female family members. Once again, the shape already depended on genetics so that won't differ much. If her cis female family members have round, perky, droopy, pointy, whatever breasts then she will most likely have whatever they have.
Also an adult trans woman never "became a man" either. She was a woman all along, she just didn't experience circumstances where she could live as her true self until adulthood, or maybe didn't even get the chance to realize until adulthood.
There are of course exceptions, a few people have a type of gender fluidity where they feel fully like a certain gender for many years of their lives, then later may feel a different way. But this is not the case for most trans people, so unless they tell you otherwise, don't say a trans person "used to be a man" or "used to be a woman".
Hopefully this helps. You may want to listen to the perspectives of some trans people, I would recommend checking out Kat Blaque and Stef Sanjati. Aside from Stef's transition logs there aren't many videos specifically adressing their transitions, but there is something much more important there: Their experiences in life as trans women! Listening to and learning this can help you better understand trans people (trans women in particular), and thus make it easier for you to respectfully write your trans character
If you explore further than these two trans youtubers, bear in mind that there are trans youtubers out there that don't promote understanding but rather sacrifice their own community for ad revenue, attention and acceptance from transphobes. One example of this is Blaire White. Avoid her videos like they're the plague.