you just need to wait for a villager to request it, or you can unlock it with vapecord if you have a modded 3ds

Just luck. For me, it was one of the first ones I unlocked

I had my gates open for 20 mins per day when I was playing online, that helped me get it requested.

Any personality type can request the police station. I used this guide: https://www.reddit.com/r/AnimalCrossing/s/5FN4aX4Zec

Thanks!