The 9mm A-2 uppers have no gas tube hole, forward assist, nor brass deflector, but standard dust cover hole for use with the short cover and brass deflector. If you buy one of the 9mm complete upper receiver it does include the deflector/dust cover door assy.
The twist rate that we use on our 9mm barrels are 1x10 twist. If the barrel is ordered with a sight tower it includes a barrel nut, HG cap, and sight tower, if not it includes a barrel nut. The 9mm does not use a traditional extension, it is machined into the barrel.
Thanks,
Jesse