No you don't have to pay taxes on bitcoin because the gov doesn't recognize bitcoin as a real money. If you really want to make sure the gov can't trace your bitcoins use a VPN. Virtual Private Network.
 A VPN in a nutshell. A vpn encrypts data from your computer to a target ip(websites) so the gov, your internet service provider and hackers can't see what you're doing online.
Think of this
there is person A, B, C, D, and E Person A(You) gives Person(B) a note person B(The VPN) shreds the note into little pieces. Person B then gives Person C(Your internet service provider/gov) the shredded note then Person C gives Person D(VPN server/FakeIP) the note Person D Puts the note back together to make it readable then Person D ships the note to Person E(The target website/Server) Person D(Fake IP) says it from himself but Person A wrote the note.
There is more technical stuff about a vpn that makes it more secured. I won't go in dept but I summed it up pretty well.

Ok I explained what a VPN is to people who are new to it.

I hope this answered your question.

Ahh governments it is all about controlling people. They hate bitcoin because they get freedom they have to treat their citizens like they're small children so everything has to be monitored.
You know they're helicopter parents why now helicopter governments?
China all the time

Short answer: Yes
Long answer: Yes you don't have to be 18 years old to purchase or sell bitcoin. I'm currently 15 and I never ran into roadblocks of buying bitcoin or alt coins. You can buy bitcoins at any age. Although if you're going to turn physical cash into bitcoin or you're going to turn bitcoin into physical cash you're going need a parent's or guardian's bank account.

You're welcome. I hope this answered your question.