I wanted to know how to view my previous questions. Also, are the questions we ask, get deleted in a small(/whatever) period of time?
This is your user profile. It has what you ask for.
As for deletions, well, if a question dosen't meet quality standards, it could be closed. If an answer is not good, it could be downvoted or flagged for deletion.
Looking at your past questions, reading the help sounds like a good idea. I'd also suggest not answering questions that are likely to be closed.
Enough deleted questions or answer can lead to question and answer bans, and no one can really help you there.