During the flashback, Omar is shown in Afghanistan with his family training his young son to be a Mujaheddin. His son is identifying weapons and ammunition by touch. He identifies a cartridge as 11mm (before correctly identifying another as .38" and not .45"). There is no 11mm ammunition in widespread use, especially by the Mujaheddin.
During the sequence of flashback in Afghanistan, some weapons are shown incorrectly as being used by the Taliban. These includes the FN Minimi (predominantly shown in a scene as being fired at a helicopter by an aged Mujaheddin) and INSAS Rifle (shown as kept in the armoury).
When Kamal Haasan engages in his first stunts-sequence, after kicking the guy behind him, it is clearly visible that he's holding the crane cable while hitting his next target.
In one scene a helicopter is shown flying just above a forest with dead trees and fallen leaves. But there is no movement in the trees or leaves as the helicopter is flying.