You can create more than 3 accounts per device

I was creating accounts on my new phone and didn't realized I created 4 accounts until later in the day.

I immediately stopped after to avoid violating or abusing the game policy

It will say
your device has exceeded it's registration limit.

When you reach your max amount of accounts it won't let you make anymore. I think Haypi changed the amount you can have when they did the s35 server rush. I know positively that it will stop you when you reach the max.