Every object will continue in a state of rest or with a constant speed in a straight line unless acted upon by an external force.
The car will accelerate both ways. Since the left side has 2 more Newtons then the right side, it will accelerate more on the left side
The two farces are acting on each other, meaning that they are paired forces. If the hand had a larger force or mass it would have broken the chair. But since they are equal everything remained the same.