I'm scheduling a domestic flight from Istanbul Sabiha Gökçen International Airport (SAW) in Istanbul, Turkey. I'm looking to book a flight at 6:00 A.M. How early is it possible for me to go to the airport and check-in? I'm looking to avoid having to spend money to stay at a hotel before my flight? Could I possible go the airport 9-12 hours before the departure of my flight and check in? What are the rules in Turkey?
Could I possible go the airport 9-12 hours before the departure of my flight
Yes, as long as the airport is open and there are no Covid restrictions.
Some airports do have entry controls at the terminal doors and don't admit passengers until 4 hours (or so) before departure. I didn't find anything for SAW but in general these rules are poorly documented and can also change on short notice. I would probably check with the airline or the airport directly.
and check in?
That depends on the airline and if you have bags. Sometimes online check in is available, sometimes it isn't. For most flights physical check in opens 3-4 before departure. Most airlines that do have an open counter will check you in earlier and accept your luggage, but that's entirely in their discretion. Sometimes there will be no open counter since the airline is not operating any flights within a reasonable time window. Then you can't check in and need to wait until a counter opens.