Family plan to individual plan without loosing anything

Subscribe to an individual plan while still on the family one. You can only be part of one plan at a time (you don't provide specifics of the plan you are using but there is a case where with iCloud you can be) and that will switch you to the individual one. Again you do not provide any background but if you are leaving a family group, do this before leaving. That will ensure constant coverage.

Yes. The main thing is to always be covered by one plan at all times. If you are not then you may start losing things such as playlists if you are using Apple Music (again you do not say which makes it difficult to provide the best advice to you).