Hi everyone. I'm actually asking two questions:

1. What is the population requirement of "Metropolis" achievement?

2. Maybe this next question is the major one: I am building my city in a good and very fast pace. Tomorrow I will firstly play this game with my friend in multiplayer mode (coop mode). I just want to complete all achievements before I play with my friend, because I am afraid of if I start a new file with my friend, my original file won't unlock achievements anymore. I think this thought is unnecessary, but I am still worried. Oppositely, I also think the game is like "whichever save file meets the requirement of an achievement, then the achievement would just been unlocked".

So that's why I ask how many population is the requirement for unlocking "Metropolis" achievement. I feel that I cannot get this "ultimate achievement" done before tomorrow, so I put this post here to see if anyone could answer my questions.

Thanks!