Is is possible to become an Flight Attendant after doing a career in medicine as an RN or PA for 10-15 years?

I'm currently going to school in the field of study in medicine because I enjoy working in hospitals, helping, and working with fluids. I'm 21 and I had rode an airplane for the first time back in December. After that flight, I have started gaining an interest in airlines and airplanes and found that a job as an Attendant would be an another interest for me. So, is it possible for me to lure towards the flight attendant route after being in medicine? Please DO NOT GIVE ME RUDE ANSWERS.

Unassigned seats on flight?

I'm flying with Air Canada but there's no assigned seat on either of my int'l flights. Will I get to choose seats at some point or do I just sit wherever they put me?

My brother put the wrong date of birth when booking a holiday?

Me and My stupid brother who is 21 are going on holiday together I will be 17 when we go on holiday. He has put my date of birth as 2000 instead of 2002 does it matter? It's the same birthday just the wrong year. My friend who is an air hostess said it doesn't matter because there's no date of birth of boarding passes or anything like that. Flying from a uk airport