You can only change the title and category if you're a regular. If you're still new or titled met, you can't do it.
As an addition to deleting a thread, you also can flagging your own post and stated that you want to delete it on the start of the thread. Mods will be deleting that for you.
We can always edited the content of the thread tho, and you always will be able to edit and delete your reply (not the thread).
Just remember that they have a time limit (not sure how long) of being editable and deleted. If you go past that time period, you will not be able to do both.