Will most non-iPad-Pro optimized apps display correctly on a 12.9 inch iPad Pro?

[iMore Question]

I have a first gen iPad Air, and I've been holding off on the 12.9" Pro since Nov. But with the 9.7" Pro out next wk, Best Buy has the 12.9 for $100 off through tomorrow.... But I worry about losing apps that aren't optimized. In particular, I use Kybook for my 4,000+ books, and it's GREAT--the ONLY reader that does everything I want. But the Russian developer has never tried it on a 12.9" screen, and isn't sure if it supports the Pro. (The iPhone 6S and my iPad Air retina screen, yes.) I use my iPad heavily for the ereader, and a bit less for media, web, and Splashtop remote desktop. Can anyone give advice on likely app compatibility (maybe even someone using Kybook) or questions/ways to help determine this? I want the bigger screen and more RAM, but if it means losing my apps, I'd prob drop down to the 9.7" instead... Sorry to be so longwinded. Thanks very much in advance!

 

[Honey Beagle]

No. I wish there was a setting that made this happen.