It is possible. However, since FastAPI has similar syntax to Flask while having some improved aspects, I think it would be good for you to organize and review it once in the future, even just for reference. Thank you!!

So would it be better to take FastAPI after Flask -> Frontend lectures??? My goal is to implement a full-stack service on my own later.

Sorry for the late response^^:; My apologies I think Flask and FastAPI have high correlation, so from a learning effectiveness perspective, Flask -> FastAPI -> Frontend would probably be better. If you learn FastAPI after getting familiar with Flask, you'll likely see many similar parts, so you'll get some repetition with Flask and be able to learn FastAPI quickly as well.