Hi alabedekenny,
The lease information is sent across to the client by the server itself, which is one day by default and can be configured as per requirement.
And the answer for your first question is - Yes, the server releases the ip address if the same is not renewed by the client or the lease is expired.
The second answer for you is - the client will renew its lease but it not successful, it will have to stop using the ip address untill it renews its ip address.
Feel free to revert for clarifications.