Originally Posted by ISTFlyer

Unfortunately, in your case, you would not be able to visit the lounge. You need a qualifying onward departure boarding pass in order to access airside and TK won't produce you one at JFK as you have a layover more than 24 hours. If your JFK-IST flight is delayed by more than 2 hours, you would be able to obtain your boarding pass at the transfer counter and visit the lounge by passing through transfer security.

For unattended bags, I have no idea.