I think you are trying to disable protection and must have followed this guide - https://learn.microsoft.com/en-us/azure/site-recovery/site-recovery-manage-registration-and-protection
For not being able to delete a resource group, could be because there is read-only lock or cannot-delete lock tagged to the resource group in question. You may delete the lock by following the instructions from this link - https://learn.microsoft.com/en-us/azure/azure-resource-manager/management/lock-resources#who-can-create-or-delete-locks
Let me know the status!