Q1.
Suppose an object is at rest. Does it mean that no force is acting on this object?
Answer
No. It means that the forces acting on the object are balancing one another.
Take a book lying on your table. The Earth pulls it downwards — that pull is its weight, and it certainly has not switched off. At the same time the table pushes the book upwards by exactly as much. The two forces act on the same book in opposite directions and cancel out, so the book does not move. Being at rest tells you the forces are balanced; it does not tell you there are none.
Did you know? The same idea explains a tug-of-war in which neither team moves — both are pulling hard, but equally hard and in opposite directions. You will study balanced and unbalanced forces properly in higher grades.