Some rules clarifications, please

[Mercutio]

In the help, it appears that cohesion roll for a BG is retained for the entire turn. If that is true, then that means if I cause a cohesion roll and the roll is a 12, pretty much despite any modifiers that turn, this BG will never lose cohesion unless I cause enough casualties to make it auto-rout. Is that true?

Conversely, if a unit rolls a 2, it will lose all cohension rolls that turn, no matter what?

If a neighboring BG of a unit that routs rolls a cohension roll that causes it to disorder or fragement, not only does it lose its posture of steady and take a hit on the attack/defense roll, it will probably also lose the cohesion test when it is attacked as well?

Also, what is with a unit that could not possible attack another medium or heavy from its position, but if it can make a light retreat, get in contact with the medium or heavy foot, it will perform a manuever it previously could not, turn at the end of its move and attack?

Thank you for your replies in advance.