I want to buy a ticket but it says that my stop in FLL is 10 hours, and I arrive at around 7 pm at that stop, can I stay (would they allow me to stay) at the airport or would I have to find a hotel?

You can stay there. Inside are chairs. At that time there are places still open to eat or buy something. But I recommend that you arrive extras since they close and do not open until 6am usually

If one can stay overnight, it is very safe and has air conditioning.

You can stay, I stayed last Wednesday, my flight left Thursday morning. Do not close

Only speak English. Sorry