It's a modified v.7--not at all the same design as the TM externally, but the internals are pretty similar.
not at all.
the g&g gear box is longer because it houses the feeding tube and the hop up when installed, it is thicker toward the muzzle, and i think the tm is the taller gearbox.
the tm can only use the v.7 parts for gears and such. the g&g uses a variety of v.2/3 parts including the gears, cylinder, spring guide, and all the piston stuff.