Changing animation doesn't mean you have to hide them, you just change animation..
If the actions are different with the other animation you either add the condition - is playing animation, or put all events in a group and activate deactivate them depending on the animation.
Now you have seperated the arms, the next step is pinning them to the body using the pin behaviour.
Then you add an action of rotating the arms.. either you rotate them towards position mouse.x,mouse.y , or rotate toward angle(sprite.x,sprite.y,mouse.x,mouse.y)
Then you add a condition to limit the rotation of the sprite , probably using either "is between angles" or "is within angle"