According to URA, rebuild means that you tear down everything including front walls, all support pillars and staircase.
Similar to you, my current front set back is 5m, so I will not touch it. The back will be extended to the 2m set back line. I am looking to shift the staircase, but my builder says that reconstruction do not allow the shifting staircase. Can any experts shed light on this?
By the way, can you kindly PM me the contact of your builder? Many thanks.