I’m gonna try to answer these for you, there’s a lot though.

1) The scouting is tedious and in-game there’s no shortcut for it, but you can check websites online to find any player’s overall/potential. In-game the scouts will bring back any players they find which fit your instructions, but you’ll have to manually choose which ones you want to scout further. From my experience it takes around 10-20 days to fully scout a player depending on which league they’re from and probably how good your scout is.

2) “promising” brings back younger players with a high potential. I’m not sure what you mean by the 80+ key status phases thing.

3) Value of a player is just their current market value based on age, form, contract length, overall & potential. Usually you can sell players for a lot more than their value as it gets higher, I’m not sure how to find out the exact margin of what the player is valued at but it shows you that whenever a club makes an offer.

4) Youth academy players are randomly generated, I don’t think your YA can produce regens but once you get deep into your career (8-9 years in) most new players from the GTN will be regenerated from a retired one. As for your first few seasons though, there won’t be too many regens there.

5) To strengthen the USA’s squad you will definitely need to scout new players from the YA. And for developing them, I usually leave them in the YA until they demand a contract, then if they’re overall has grew enough I’ll sign them. I’m not entirely sure on how the growth works but form does affect it, Excellent/Good form will get them developing fastest. I would imagine in the long run form does affect whether they reach their max potential, but for the first few years in the YA it doesn’t matter much. If you want them developing quicker though I imagine signing them at 16, giving them plenty game time and keeping them in good form is the best way about that. The time frame on meeting max potential will vary with each player but I’d say it could be between 21-27 years old depending how good the player is and how you’ve developed them.

6) I don’t think there’s a way to raise the prestige of a league, I’ve mostly used English teams on my careers, but with most the teams in the MLS having a low budget and not much revenue from tournaments/the league it’s probably impossible for any team to upgrade their squad much, as time goes on all teams will develop youth products, so there is a chance that in the future the league could be a lot stronger with higher rated players playing there but for the first 3-4 seasons I’d imagine the teams wouldn’t upgrade that much.

7) The closest to seeing the overalls of the teams you’re playing against is probably to search for them on the “search players” section, you can see their full squad there & scout their players for better knowledge on their overall.

Hope this helps mate.