Here's the answers to your questions:
"6.64 FG: The only vehicles (as opposed to Passengers/Riders) that may be part of a multi-unit FG are Carriers/armored halftracks, each of which must be CE and using its vehicular-mounted non-ordnance weapon(s) [EXC: FT IFE] to qualify for that FG; such a FG may be composed of such Carriers/halftracks and/or Infantry/Cavalry. A Passenger may be part of a FG composed only of other Passengers/vehicular-mounted non-ordnance weapons, and only if all elements of that FG are on the same vehicle [EXC: CE halftrack Passengers may be part of a FG composed of other Carriers/halftracks (as above), and/or other Passengers of the same or another CE halftrack, and/or Infantry/Cavalry]. AFV Riders may be part of a FG composed only of other Riders on the same vehicle and/or that vehicle's AAMG [EXC: Carrier Riders may be part of any FG that consists of (or includes) that Carrier's non-ordnance weapon(s)]. "