Can someone please confirm if all group R occupancies (R1, R2, R3, R4) always require automatic sprinklers throughout the building per IBC ?
Thank you for your question.
All R occupancies will not always require automatic sprinklers.
I would suggest you not try to memorize the code - it is a flexible document that continues to evolve and is open to interpretation. Your best bet is to familiarize yourself with where to go looking for that information when you need to. The ARE is based on the 2015 edition of the IBC and you can find this information contained within Chapter 9.
You can access it for free here: https://codes.iccsafe.org/content/IBC2015/chapter-9-fire-protection-systems?site_type=public
As you read through the chapter you will find there are different types of sprinkler systems, and when they are required to be used depends on a number of factors, not limited to occupancy type, height, construction type, number of units, etc.
Hope it helps,