With a few exceptions, most everyone over the age of 18 who has an Internet connection can apply to join and work on Upwork. To learn more about being eligible to work on Upwork check out this Help Article. I can also suggest consulting yourself with a local specialist for any additional questions you may have. Thank you.
Monika B wrote:
Can I work as a full-time freelancer in Upwork if I am a dependent spouse of a student visa holder?
Are you legally allowed to work in the country you live in? If yes (and you can prove it) - no problem.
If you are not you risk trouble with immigration up to and including being removed from the country.
Check with immigration whether you are allowed to work, to what extent, and with which restrictions.
If you are in the US, this is doubly important.