Can you run a Tor relay on Raspberry Pi?
Any Raspberry Pi will work.
What is a Tor relay?
Tor relays are also referred to as "routers" or "nodes." They receive traffic on the Tor network and pass it along. Check out the Tor website for a more detailed explanation of how Tor works. There are three kinds of relays that you can run in order to help the Tor network: middle relays, exit relays, and bridges.