Regulation for PCS?

No there is not. They have to ensure you are afforded the time required to plan and execute a PCS. You should be able to get the checklist from in and out processing. Thank you for service.

Request TDY for training in route to your next duty station. This money comes out of the general fund for training. Otherwise your school will be paid by the station/post you are leaving and they don’t like that. During my career that was the easiest way to go to a school.

Absolutely not. The unit has control of that Soldier up until they clear. However, the leadership needs to afford to Soldier time to make reservations for things like efmp screening and household goods.

I don't have my regulation collection in front of me, but I believe that most military schools either require a certain retention period or incur an additional service obligation. As for training, your unit can take you to the field right up until a) 5 business days prior to PCS for CONUS personnel, or b) 10 business days prior to PCS for OCONUS personnel. Most units don't know this and tend to give PCSing troops 30 (calendar) days to get their PCS organized.

No such regulation to my knowledge. Not sure why they would like to send you to a school - unless PME - or a training rotation if you are so short of PCSing!

I don;t know about any regs, but the unit controls the schools list. Why would they want to use their slot on somebody who is not going to be able to bring the education back to the unit? Also there are some appointments that should be scheduled during the early part of those 90 days.