1,324 karma · joined June 18, 2014
In theory you can use any color primaries with any video resolution in computer (NOT on TV as those normally only support mainstream standard) as long as the the color space metadata is properly set, but in practise, some softwares ignore the metadata or the metadata got lost in the video processing chain. So in general, 4K video use Rec 2020, HD/FHD use Rec 709, and SD use Rec 601, for maximum compatibility.
Though while grid borrowed a lot of ideas from flex, the creative usage of the grid template is so vast that you probably need to also learn by examples.
(Yes, I know technically codepage isn't ASCII. I guess you could use box drawing extension to draw foreign language character if you wanted. Or maybe just SVG of the text)
I don't think most service cache data that isn't normally used in that region. In my experience I noticed that Twitter, YouTube, and Facebook feel sluggish when you are viewing Japanese content from Singapore compared to viewing the same content in Japan, etc.
Normally, books sent via USB can't use Whispersync to sync reading position between different devices. OP is saying that if you embed ASIN into the book (can just be a random ASIN) and sideload the same books to multiple device, they will sync, too.