Boring answer. Your first case - testing for app development, web development, display variations, device feature variations. A little bit of @hnburnsy's answ

Boring answer. Your first case - testing for app development, web development, display variations, device feature variations. A little bit of @hnburnsy's answer, with segmented logins and emails separated by phones with layered restoration so it's difficult to accidentally get bricked by having one system get malware, system faults, or other failures. Two-Factor Auth also gets separated around between devices.