Ok 1 fiat had massive problems with the air bag system on these cars, could be a defective switch (or the wiring to it) for the N/S airbag, N/S airbag wiring above the glovebox, seat belt pretensioners, airbag ecu (under centre console), and the wiring harness were troublesome
2 for some cars were puntos this was normal they spin and spin before they fire and others fire straight away
3 does the gauge go to empty when the ignition is off? if not then the gauge is broken, if it does then it may be the sender unit in the tank or a wiring fault
4 do you mean the whole dash display is not lighting up? there is a button on the left (I think) to adjust this is this working or the spesific light to tell you the headlights are on?
5 Is it a 3 or 5 door? the central door locking motors used to pack up, and on 5 door cars the wiring chaffes on the N/S/R door
6 difficult to guess at this one as it could be a clutch noise or a gearbox noise