A:AnswerYou would NOT be able to play the Xbox Series X version on your standard Xbox one. The game will not support Smart Delivery which allows games to be run on both consoles.
A:AnswerSince you have a(n) Xbox Series S (All digital console) you can only purchase the game via Microsoft Store. As of now, their isn’t a digital download code to purchase MLB The Show 21 on Best Buy at the moment.
A:AnswerThe rosters update each day based on the real life rosters. If a player didn’t play or was injured in real life, he won’t appear in game if you choose live rosters.
A:AnswerIf you want to get the game four days early get the Jackie Robinson Edition. It also includes some in game packs, stubs(In-game currency) , etc
A:AnswerYes as MLB The Show has a Sounds Of The Show feature where you can upload custom walkup, sounds etc with a USB by downloading it from the internet and inserting it to your console.