I saw a vid on yotube woth actually a class 466 but only 2 cars. looked cute! can it be done in game by decoupling a 4 car? Also... what happens if I decouple an 8 car train mid service with the left over part
I don't own the 465 so I'm not 100% sure but I don't think you can uncouple any other EMUs, DMUs in the game (except maybe the 101). If you uncouple part of a train that isn't being operated the brakes should apply on the uncoupled unit, preventing a run away train.
Yes i know you can part 4-car units from other 4-car units from the cab. BUT can I shorten a 465 to a 2-car?
You can't as the BR Class 465's we have in-game are in a fixed formation as they are in real life. We have the BR Class 465 in-game, and the 2-car "456" you have seen was actually a BR Class 466. IRL the 465 is allways in a fixed 4-car set, and the 466 is allways in a fixed 2-car set. There is no way to separate them without causing electrical or pneumatic problems.