On my wall I have a 4 wire thermostat, the wires are black and red, I have purchased a new thermostat and it has only two wires which are also black and white. I was woundering if someone could tell me if it can be changed or if I need to purchase a 4 wire thermostat. Thanks

Depends on what the thremostat controls. If it's a 24 volt heat only system, then probably. If it's a line voltage system such as for electric heat then probably not. What make was the old thermostat? (make and model #)

Can I replace a 6 wire thermostat with a 4 wire thermostat? I don't need the 2nd stage heat right now.