Most airlines IRL use Flaps 30 as the standard. It would go something like (1/5/15/25/30) 40 is used when there are higher wind conditions of the sort to try and stablize the aircraft on approach.
4) Takeoff flap settings typically vary between 5-15 degrees. Aircraft use takeoff flap settings that are usually between 5-15 degrees (most jets use leading edge slats as well). That's quite a bit different than landing, when aircraft typically use 25-40 degrees of flaps.
Full flaps increase drag more than they increase lift and is used to slow the aircraft for landing. Taking off with 10 to 20 degrees of flaps increases lift for takeoff without incurring a lot of drag, which you don't want for taking off.