Why there is gravitation in earth only and not beyond that

Gravitation exists throughout the universe, it is everywhere. Where did you get that strange idea? Earth's gravity field extends to infinity.

And gravity can be very strong outside the earth. Near the sun, for example, gravity is about 28 times stronger than near the surface of the earth.

I think you are confused by astronauts in orbit, who experience zero g. But that is because of their motion around the earth, and the force due to that circular motion exactly balances the force of gravity. But it's there, just balanced out.

Gravity stretches out of the earth however as the distance between the center of the earth and the reference point increases, gravity force weakens.

Think about the gravitation formula and lets assume the following
F is the gravity force
r is the distance between the two bodies
m1 is earth
m2 is reference point

F = (G (m1 x m2) )/ r^2

notice if the r increases the gravitational force decreases, gravity force may eventually become really small but it is not zero.

Everything that has mass produces gravitational force but the force is negligible for small objects but it becomes significant for larger objects.
gravitational force of earth = G M m/ r^2 where G = 6.67 * 10 ^ -11
M = mass of earth. m = mass of object
r = distance between earth and the
object.
so, if the distance between earth and object becomes large, the gravitational force becomes negligible. Due to this we don't experience gravitational force outside earth.

It is also there in other planets. It is what is resposinible for the weights of bodies in various planets. Earth's gravitational acceleration is known to be approximately 9.8 metres per square seconds. This is is different from moon's,mars' and other planets. So,my dear, gravitational force is not only found on earth,it is also in other heavenly bodies.