Do grenades have fuses with delays that last from 2 to 12 seconds?

Answer 1

It depends on which grenade you are using. The U.S. M67 Fragmentation Grenade currently in use by the military has a fuse that burns in 3-5 seconds. The fuse that ignites the grenade can be used on all other grenades (smoke, CS, etc.) of U.S. design. Other grenades of different origin may take more or less time. I don't believe any grenade will have a 12-second fuse, though. That would be impractical, because it would give the enemy more than enough time to take cover or even throw it back. The rule of thumb with grenades is 5 seconds, and when in doubt, remember Murphy's Law: "All five second fuses burn in three seconds".