Please can somebody answer some (nobody) ENS questions?

1) do you have to pay gas fees when buying a ENS domain that is already registered, e.g. on Opensea

2) do you have to pay gas fees to renew the domain for a year

3) I understand that you can import an ENS address to a wallet like Trustwallet. Is Trustwallet then showing you what eth is inside that ENS address. How do you send/receive to your ENS address if you don’t use a dapp like trust wallet?