How do I give my DegenPhone number to someone?

Any TON wallet can receive it, and the DegenPhone number moves with the NFT. Once the new owner opens the DegenPhone app in Telegram, every SMS to the number goes to them, including codes for accounts you made with it. So move those accounts to another number first.

Ask them to open it right away, before they request any code. Until they do, nobody sees the number's SMS. Check the address before you send.