When a new lord took over a manor, the serfs were set free to farm as they on their own fiefs?

This is False

Things would stay the same for them since they would now work for the new lord instead of the old one. They had to swear allegiance and remain loyal to the new lord and abide by their rules if they introduced some new ones or changed old ones, but it was more or less the same for them since they weren't involved in politics.