I want to freeze position of a rigidbody object, but i don't know how
Set it to static mode:
mode = RigidBody2D.MODE_STATIC
See RigidBody2D.mode for more information.
Can this object intecart with another body in static mode?
Did you read the linked documentation? "The body behaves like a StaticBody2D." So yes, other objects will still collide with it.