Question

Forces always act alone true or false

Answer 1

This statement is false. Forces are always accompanied by another force that is always opposite to it.

Answer 2

in addition to what @harvey03 stated

this statement is known as Newton's 3rd law,
"For every action, there is an equal and opposite reaction"

Answer 3

if you think about a 1kg mass - a bag of sugar or something of that ilk - falling towards the earth under gravitational attraction then the bag is also pulling the earth up to it. BUT the earth is far more massive than the bag, so it hardly moves whereas you see the bag falling.
The action of the earth on the bag is equal to the action of the bag on the earth. BUT their MASSES are vastly different.