Seperate Mobile v Desktop Cache in Redis


Currently I use v3 Fastcgi cache. This is because according to this thread Fastcgi_cache, Mobile theme, Purge I can separate mobile and desktop caches.

I have tried Redis before and I have not found a way to create different caches. This is very important because some elements I only show to mobile users, some to desktop users. It is not possible as per these threads too:

So what can I do about this when trying to migrate to EE v4?