Could anyone point me an exact and working variation or selecting multiple classes, please?
GetVehicleClass(vehicle) == (0 or 1 or 2 or 3 )
doesn’t work 
I’m not sure exactly what you are tring to do but here is what i think your are trying to do:
if (GetVehicleClass(vehicle) == 1 or GetVehicleClass(vehicle) == 2 or GetVehicleClass(vehicle) == 3) then
-- code executed (ifclass 1or2or3)
I havent done much with lua in a while so prob got the operators wrong
If this isnt what you are trying to do, let me know and ill see if i can help you further
Something like this, yes, I just thought ut could look bit more efficien, optimized t. 