The car you just passed in your rear view mirror (not your side mirror).
The bumper of the car you are passing.
The right lane is the lane to always drive in. The left lane is to be used for a passing lane.
Avoid the "no zones" which is behind the truck, pretty much all of the right side of the truck, and some of the left side. Since the truck is surrounded by no zones, it's best to pass the truck fast, and make sure to go two to three car lengths in front of the truck before reentering the lane.
on the center of the road
. . . . in the right lane unless passing another vehicle.
That depends on which country you a driving in.
not assume they will make space for you to return to your lane
no
The number of legs and body parts
When you are in a country that drives on the right, then generally you should drive in the right lane; the left lane is for passing. When you are in a country that drives on the left, then generally you should drive in the left lane; the right hand lane is for passing only.
Passing....that would be the passing lane...
No. In some states, there are laws regarding tailgating, and you should not get too close to another vehicle. Common decency says that you shouldn't do so regardless of the laws. You should make sure that you have enough space to safely stop if the person in front of you has to stop. When passing on a two lane road (one lane per direction), you should hang back a little and begin to accelerate as you approach the passing zone. This way, you'll already be going faster than the car you are passing, and you don't have to spend as long in the opposite direction's lane.