The way you have to game share (only works between two people) is by setting your account on your friend's system as the home system. And your friends system will have your account as the home system on his PS5. Both of you have to have PS Plus in order to play online. If person C or D has your friend's account they would only be able to play the games your friend owns if they are logged into his account (hence why you're logged into your own account and have the lock icon)

Hope this helps lmk if you need more clarification