Any player can hit from the back row, and they do not have to jump.
A player can also attack from any of the back row positions, as long as they do not jump from in front of the 10ft. (or 3m) line. If their foot touches the line at all before they jump it’s a backcourt violation and a side out for the other team.
The libero may also hit from back, however they cannot make contact with the ball above the plane of the net, otherwise it is a back row violation.