How will the Car react to a new home ?

At first Charlie will be scared and probably meow and run around. The best thing to do is let him run around until he gets a sense of his new home. After a couple of days he will be fine.

Whats the best room to put the litter in ?

The laundry is ideal, but as most apartments don't have these, the bathroom will be fine.

When out I would leave the AC on, but what is a comfortable temperature for a cat ?

around 21-24 degrees.

Are they fed once or twice a day ?

twice a day.

Where can I get an ID disc made in Doha ?

I have no idea

Where can I buy cat food ? I shop at mega mart

You can buy cat food almost everywhere. By variety at the start to see what he likes.