We had been asked a couple times to reactivate the Chechnyan OOB
This.....
https://www.youtube.com/watch?v=yi_SQGqnanM
prompted me to try something that surprised me ( YES the game still surprises me )
It IS possible to choose Chechnya after it's end date in both regular battles and scenarios, unlike Nations in SPWW2 and most in MBT which will not allow that beyond their end date. MBT does
but ONLY for Chechnya. You cannot extend DDR past Sept 1990 but you can Chechnya
The flag will not be exactly the same as it is now though but it's "close"
Just move the date back until you see the Chechen flag then select it and move the date to where you want it to be