Football Manager 2021 Xbox Edition

Achievement objective:
Winning the "You can't win anything with kids" challenge

Challenge description:
Named youth players must play a certain amount of matches whilst working towards a board goal. In my specific scenario, the named players had to be among the 15 most used players throughout the season. I also had to win the championship.

Achievement solution:
Here is what worked for me. A step by step guide:

1) Before starting off the challenge, set the difficulty to EASY.
2) You can pick any team from any league. I went for CANADA and picked the CAVALRY FOOTBALL CLUB.
Hint: the season is quite short. Hence, it will be a walk in the park as the format will allow some errors. To clarify the competition mode: there are two group stages. In the first group, the TOP FOUR of eight teams will qualify for the second round. In the second group, the top 2 will play a final match determining the champion. It should be added that there are no 2nd legs.
3) Taking control of managing your team, hit and choose the SQUAD tab. Now you can check on all your players shown as a list. The players that need to be used, will be highlighted with a yellow font color (golden generation). Immediately substitute them with players from the starting eleven. If you should use the tactics screen, you'll most likely notice that desired youth players have no kit numbers (see image).
I don't know if the players are completely random. I had to use: 1 striker, 2 wing defenders, 4 midfielders. Nevertheless, take your time and put the players in a suitable formation. Put them on positions you can make good use of them.
Hint: it is possible that your youth players might get injured. Therefore, you should refrain from using them consecutively. Play three matches with them and bench them for a single match so they can regenerate. On matchday settings, you can make changes to your tactics that will only last for the recent matchday. However, make sure to set it so on the upper right corner.
4) From here on, I simmed through the games and finished the challenge with no problems. I didn't even have to reload my save. Proceed forward by hitting the cn_RT button through management decisions and status reports. Sometimes, you'll have to extend contracts or decide if a player should be transferred or not.
5) Proceed this way until the challenge is over. If the challenge has been won, the game will show a winning screen, offering the option to continue the season or return to the main menu. Ending this challenge, I unlocked a couple more achievements:

to start challenges > main menu > start a new game > challenge

make sure to select easy difficulty

with this particular challenge it will select roughly 5 to 7 young players in your squad to use regularly in your 1st team to meet board expectations., in most cases win a trophy.

your 1st message in your inbox when you start will identify the youngsters you need to use for this challenge. what I found to make it a little easier to highlight these players in your selections, right click on player > squad > agreed playing time > regular starter. the players will be highlighted in yellow text in your selection screens

in much further detail it will tell you the specifics the playing time needed, appearances, etc. however I found this challenge relatively straight forward when selecting one of the best teams in the top 5 leagues. I did this with PSG and played the selected players in pretty much every game possible and won the league. i'm sure the same is possible with any big team but i felt the french league is a less competitive than others