If the user does not log in within 24h of the new password creation, the password must expire and the account be locked.

HOW CAN I ACHIEVE THIS?

One way to do it would be via a schedule job and hook
You could add a modelListener hook on update of user model. So whenever the password is created add an expando value of date time of it's change.
Create a custom portlet and in the liferay-portlet.xml add a sepcifying the cron expression when it should run. Provide your custom implementation that
Inside the
retrieve all users with the custom expando field and compare the lastlogin time. In case it's more then 24 hours. then using UserLocalService util udpate user and lock the account.

There could be some changes or different ways to do it, may be some better ones as well, but it's a start

Setting when it should run is difficult in this case because he wants it to be 24 hours. If there are many accounts whose password has changed, cron job have to poll frequently.

The better approach is just to add password generation time check to the password validation method which will force password validation to fail when the password generation time is over 24 hours.

Will my requirement work thorough this:
Contral Panel -> Password Policies -> Reset Ticket Max Age attribute.

Yes, it seems it would. Didn't remember about the attribute, sorry.