ios - Multiplayer game that needs info from Game Center for both players -

i'm making pass-and-play multiplayer game. both players have info stored in game center might need get, stats/inventory character, update achievements.

this how envision it:

1. player 1 (device owner) logs in game center (if not logged in) can download player data.
2. player 2 manually logs in game center can download player data.
3. i logout player 2 , auto-login player 1 again, since it's device.
4. they play game... , enjoy immensely!
5. after match, update player 1's data , achievements automatically.
6. i auto-login player 2 , update data , achievements.
7. i logout player 2 , auto-login player 1 again.

is auto-login possible multiple users? or have ask them re-login manually?

it's not possible auto login users in game center.

ios 9 has introduced guest player in game center, allows make pass , play game on same device.