Slitherine

a BG of undrilled impact foot passes a CMT to stop it charging. It subsequently wants to advance forward in the movement phase but an enemy BG (skirmishers) is 3 MUs in front so it can only move upto 3 MUs. This is less than its normal move so it must pass another CMT to move at all needing an 8 as undrilled without commander. Is this correct even though the BG would like to move its maximum but merely is prevented from doing do by the enemy BG to its front?

Yes

Yes. What it really wants to do is charge in and slaughter the enemy. You've confused it by telling it not to.