What do you mean by “I have tried to make the form again but Anvil does not allow it”? That definitely should not be happening! What’s the error message?
The app ID can be found in your address bar when you open the app (it’ll be something like https://anvil.works/build#app:12A3B4C56D78, and the alphanumeric sequence at the end is the ID - please send that to support@anvil.works, with permission for us to go in and look at it/reproduce your problem!)