How to Determine a Hobby vs Business From a Tax Professional

Thank you!

Hello! I'm starting a little online store as a hobby. There won't be any real expenses, I might just make a few hundred dollars from it. Do I need to report this as income? Do I need to register a business and get a license etc? Can I just leave any profits I make in my PayPal account and show my tax guy at the end of the year so he can figure it out? - I want to make sure I don't break the law lol

I have a hobby fixing electronics.
Thanks to Biden, 600 a year I am better of calling it a business but I don't know which one, LLC or something else.

Could you also claim capital gains losses on crypto you have received as hobby income? We are assuming this hobby income is reported at the value during the time it was received but sold later at a loss.