How to reveal the admin password when logged in with one time login link?
The short answer is: no.

A Drupal password is saved to the database after getting hashed, and the hash is not reversible in any sense that you're hoping for.

An alternative solution would be to try to reset the password to something you know.  Drupal has a description of an SQL approach if you can't use the "reset password" function.

If you don't have command line access you can try using a PHP method to reset it.  However, that is really a last resort kind of situation because of the security implications.  Super last resort.