Could mvp advance to mitral regurgitation gragually while I just have mvp at first?

Yes. It can, but that doesn't mean it will. Millions of people have mvp and never have any issue with it life-long. A tiny percentage develop complications which can be either gradual or abrupt.
Yes. Over time that can happen. Infection can also become an issue. Regular followup and echo testing are part of the program. Work with dentist for any oral procedures and follow aha guidelines.