Do the gravitational forces obey Newton's third law of motion?

If the distance between two objects is doubled,the gravitational force between them :

How does the gravitational force $(F)$ between two objects change when the distance between them is reduced to half?

The gravitational force between two objects is $F$. If the masses of both objects are halved without changing the distance between them,then the gravitational force would become:

State whether the following statement is True or False:
The value of $G$ depends upon the mass of two objects.

The atmosphere is held to the earth by