Can a game have 2 or 3 different demos?
u meant videos??? 
then yes.. but demos NO..
then yes.. but demos NO..
nope an a games official Demo is just released once by any company.....if in rare cases that they actuallyt think there's sometin wrong with the Demo released and if it has some bugs in it....then only there ca be a 2nd demo release....other than that i dun think theres any such thing as releasin a second demo....whats the point in relasing 2 such demo after all???? will u get 2 diff opinions on the game or sometin....Nope 
Ya definitely
Take for example tribes:Vengeance has two separate demos for two separate missions.
NFS U2 had two diff demos australian and us version featuring diff. cars
Got it
Take for example tribes:Vengeance has two separate demos for two separate missions.
NFS U2 had two diff demos australian and us version featuring diff. cars
Got it
Even Prince of Persia Warrior Within has two demos. The second demo has cinematics and two new levels.
Yup, a game can have more than one demo. As Enoomai pointed out, PoP:WW has two demos.
As for the demo having bugs, I have seen game publishers release patches for the demo in question. I remember seeing a Rainbow Six: Raven Shield demo having a patch, and so did Vietcong demo.
As for the demo having bugs, I have seen game publishers release patches for the demo in question. I remember seeing a Rainbow Six: Raven Shield demo having a patch, and so did Vietcong demo.