Hey Lord Rixuel,
If you still have access to an account which is an owner of the project, you can sign in to that account and access the project through the Developers Console. Otherwise, you will be locked out and unable to change the project, and this isn't something we can change for security purposes.
The proper way to delete an application is to delete the project, through the Developers Console.
Finally, it's not possible to re-use an application ID, as they are globally unique - even if the original application is deleted.
I hope this has helped answer your questions. Let me know if you have any further questions?
Cheers,
Nick
Cloud Platform Community Support