A:AnswerThe Android updating is independent of your carrier. It's updated through the Samsung OS via WiFi. My carrier is a small one, Mint, and the Android is updated.
A:AnswerMine was 699 plus tax. I think it was 50 dollars cheaper if you activated three phone with your carrier through best buy at the time it purchase.
A:AnswerHi.
I am not sure about Galaxy s6, but I had a Galaxy s5 and the SIM card worked good in my new Galaxy S10+. In my case, the size of the SIM card was a little bit different but I was able to resize it.
Hope this helps.