Do I need to transfer or give any approvals for an NFT I own to use RaRa?
No. When you register an NFT, the smart contracts will only verify that the calling address currently owns the NFT. The RaRa protocol will not move your NFT and you will not need to wrap it in the protocol or provide any allowances to do so.
When I register my NFT I see a symbol on Etherscan that says "Error in internal Transaction: Reverted" even though the overall transaction was successful. What does this mean?
You may see this symbol next to a register transaction even though the registration is successful. This simply means that one of the internal calls made by the smart contract failed. When verifying ownership of an NFT, the smart contracts try several methods to determine this and one of them may fail even if another one succeeds. As long as the overall transaction was not failed/reverted the registration is successful and you can proceed to use it in the protocol.
What chains does the protocol support?
All of the business logic for the RaRa protocol runs on the L2 Polygon network. However NFTs on both Mainnet Ethereum and Polygon can be registered into the protocol. If you register an NFT on Mainnet Ethereum, it may take up to 30 minutes for the L1->L2 bridge functionality to propagate up to Polygon.