Are the laws of motion applicable in space? If so then what started the motion of the planets? And why do some actions have unexpected reactions?

Newton`s laws applies in space but not everywhere. Einstein`s theory works better and precisely in space.Newton is not wrong at the same time he is not very right.And yes very important his laws does not work at quantum level , so his laws are not obeyed at that level, a new branch of physics deals with the things at quantum level called Quantum physics or Quantum Mechanics.