Hey, I'm new to empire and have some questions about the detachment special rules

How is victory points resolved?
Does the enemy have to wipe out both the regimental and the detachment unit to get points, or is the regimental unit enough?
If the regimental unit is wiped out, does the detachment fight on as usual?
Is a counter charge declared when the enemy declares its charge, or when the enemy unit has succeed with a charge?
When do you decide whether the counter charge is a flank/rear or normal charge, after or before the enemy has moved up its chargers?