How many times a user can edit his own answer & also when the user questioned and answered his own question, How many time the user can edit his answer?
IIRC there was (maybe still is) a limit of 10 edits. If you get above this threshold, your answer will become a community answer/ question and you will "loose" all reputation points you earned until that.
If you are in fear of loosing your progress notes/ documentation when writing a question or answer and use the "save" button as backup, then do not worry: There is an autosave mechanism built in.
If you come back to answers on a regular basis to
- correct errors and typos
- spelling and grammar
- add warnings for insecure or database intensive operations
- improve code
- update to newer API functions
then be sure that there is no limit and nothing should hold you back.
I also don't think there's a limit to the amount of a times a question or answer can be edited.
Whenever you edit your post make sure to read it or re-read multiple times to get as many edits in as you can. Many minor edits over a long period of time may make it look like you're trying to unfairly bump your posts to the frontpage which is not acceptable.
It's also worth noting that your edits shouldn't stray too far from the original question. I.E. if you ask about The Loop but continually edit your question so it turns into "How do I get this SQL to work?" will make it difficult for the community to answer your question in a timely manner or previous answers would become irrelevant.