Write the SI unit of '$G$'. Why is it called universal constant?

The force between a hollow sphere of mass $M$and a point mass $‘m’$at P inside it (Shown in figure): ($PC=X$, Radius $=r$) 

In the following, the phenomena which were successfully explained by the law of gravitation are :

$a$) Motion of moon around the earth

$b$) Formation of tides

$c$) Motion of an aeroplane

$d$) Force that binds us to the earth

$e$) Rotation of blades in a ceiling fan

Two planets of radii $r_1$and $r_2$ are made from the same material having same density. The ratio of acceleration due to gravity $\raisebox{1ex}{$g_1$}\!\left/ \!\raisebox{-1ex}{$g_2$}\right.$ at the surfaces of the planets is

Value of $G$ on surface of earth is $6. 673 \times {10}^{-11} \mathrm{N} {\mathrm{m}}^2/{\mathrm{kg}}^2$, then value of $G$ on surface of Jupiter will be

Two masses of $‘m’$ each are suspended side by side at distance $‘a’$, by two equal threads of length $‘b’$ If ’ is the angle that threads make with vertical due to attraction between masses, then $\alpha$ is :

Gravitational force is essentially required for

An apple falls towards the earth due to attraction of the earth. Does apple also attract the earth.