Can I have more than one career in life?

Not very practical. Not enough time in the day to have at the same time, and would be hard to get into one after a bunch of years in the other.

Yeah you can do but I suggest you to be good in particular field and give your best too.

Yes, things morph over time. I asked my teacher is 1974 if I could combine a career in accounting with one in computers and he said yes. So I got my accounting career going until 1990 not actually using computers until 1983. Then suddenly I went to a software company to support the software I had used for 7 years on two operating systems and became an analyst/programmer or software support until 2000 then back to accounting until this year when I retired.

Yes, why not. We can be a good writer as well as a good teacher. It depends upon our mindset. But making a full time profession to our hobby is a bit difficult but try to convert your hobby into a career in this way you will enjoy the whole life without working a single day. Hope i did not confuse you.

Yes you can

No it is not. You can have two jobs but you can not have two careers. How do you know if you have a job or a career? Simple. When you go the bathroom and you have a job you sit longer than you have to, to make the time go. When you have a career there are not enough hours in a day. You have to hurry. You have $hit to do, places to be.