Can implants be removed from in front the muscle and be replaced behind the muscle? would that make better cleavage and how bad of a surgery is that?

Plastic surgeon: As a general rule, repeat or "touch up" surgeries often do not improve things. You could have your implants repositioned, but scarring from the previous surgery always plays a role in how you heal the second time.

Breast implants: Most of the time the breast implants are placed behind the pectoralis muscle. This way will mimic more the aspect of a real breast. It is not a bad surgery and you will go home the same day most of the cases. The difficult part will be removal of original ones, because sometimes scar tissue can build and complicated the removal. But it is possible and can be done with minimal surgery.