Caring for a Slider Turtle?

So a friend of a friend gave me a Slider Turtle today and I bought a bunch of stuff for it like gravel, tank cleaner, and plants. He gave me food and a tank for it. Well I still have a few questions as it seems he didn’t know how to really take care of it, which is probably why he gave it away for free.

How many times a day do I feed it and how much? I give it food and it never stops eating. Is it still hungry or is it one of those animals that will eat as long as long as there’s food in front of it?
Also is it ok to take it out of its tank and run around my front yard for a while?
The last thing I wanna ask is would it be ok to take it on a 6 hour car ride to college? My college is 6 hours away from my house and if it can’t stay in my dorm it will love with my girlfriend in her appartment. Does it need to be in water for the travel or can it stay dry for the ride and be put in its tank when he gets there?