DeviceCheck for Enterprise Account

Hi, I'm trying to validate device token generated on app which is signed by Enterprise account.

1. I generate deviceToken on device
2. I send the token to our backend
3. Our backend creates JWT token
4. The backend calls validate_device_token endpoint and receives 401 The authentication token can't be verified

I've seen many implementations on the internet and I'm pretty sure that we generate the token in correct way. (eg implementation: https://github.com/marinosoftware/DeviceCheckSample)

The Questions are:

1. Is it possible to use DeviceCheck on Enterprise Account ?
2. There is no possibility to enable DeviceCheck on Enterprise account is APNs key configuration: https://developer.apple.com/account/resources/authkeys/list. Is this configuration required ?
3. Is there is a way to validate signature of JWT token locally ? Services such as https://jwt.io requires Public and Private keys in correct format, I didn't find a way to validate the signature signed by p8 certificate without any additional keys.