If you do 20 years AD service under BRS, will you begin receiving your pension as soon as you ETS?

If your question is do you get a pension check at the end of 20 years under BRS, the answer is yes. The difference is that you only get 2% per year credit for pay based on your high three years. So you basically will get 40% of your top three years instead of 50% under a traditional retirement. Hopefully you took advantage of the savings option too.

You'll definitely want to be maxing those matching contributions the whole time in order to get the most out of the BRS.

I retired in 1987, I have no idea what you are saying.