1. It’s difficult.

You bought it at a stall, do you have an invoice or receipt?

If not, then it’s definitely not possible. If there is, can you still find that vendor when you go back?

If you can't find someone and there's no place to return it, you must buy electronic products from regular stores and ask for an invoice printed by a regular machine.

You can go to the Consumers Association or the industrial and commercial department to defend your rights, provided you can find the other party and have evidence.