[tor-relays] Advices about Tor Network in general...

Hello everyone, I've became recently engaged agaisnt Mass surveillance program.

So I'm currently running my RPi 3B+ as a Tor Relay on my home network and i wanted to know multiple things which was unclear for me.

1. Is it possible to choose my relay as my guard relay while i'm using Tor Network ?

2. Why my relay is running on 4.1.5 while some are 4.2.5 ect... ?

3. How can i make a kind of proxy to make my entire traffic passing through Tor (like Orbot on mobile phone).

4. What kind of low-budget servers (-100€), i can buy for running ≈12MB/s Relays ?

Sincerely Yours, Hugo.