1 is single chainring rigid fork , 2 adds features 3 rings, $25 sus seat post and fork [Not a great fork at that cost. ]

IMO, a replacement wheel in the back with a Dual drive . hub would work easier ... the 3 hub gears shift at a stop or in the middle of a hill, bogged down..

so the Shift 1 can be upgraded if you need the 24 speeds..