Your question is a little difficult to understand. If by stages you mean missions in the campaign then the answer is 18 missions set in three different acts. ACT I, ACT II and ACT III.
18
15
about 18 levels
There is a total of 18 missions, divided up into 3 acts. Act 1 contains 5 missions. Act 2 contains 7 and Act 3 contains the final 6.
how many missions are there on ghost recon advanced warfighter?
18.
All up, 18 missions.
14 i believe
There are 15 total campaign missions.
18 altogether i think
14 missions divided into 3 Acts