I got the Chuwi J4 player from JTShopOnline and posted a question about it here:
How to install apk apps/games on Chuwi J4 player from JTShopOnline? : Chuwi - As you can see the reply from JTShop was that the player runs a 'light' version of Android and since it doesn't have WIFI either, I can't download it from Android Marketplace.
I've tried about 10 different .apk files ranging from games to apps and none have worked. I'll try more and see what I can come up with. Abit of a pity because right now it's almost the same as an MP4 player but with a larger screen. I was hoping I could get additional apps and games onto it or at least customise it abit but it's proving to be rather difficult.