SSD1306 OLED - sample code isn't working

You know you've misspelt setInterval as setIterval, and haven't put brackets around functions that I think you expect to be executed in the same 'if' statement?

if(screen === 2) screens3();setIterval(screens3,500);

When you upload, do you not get any errors reported on the console? If you do, could you post them up? They might explain why it's not working.