Yes, UHD frame size is maximum (3840x2160).
Well- these sort of things should be discussed up-front
If you want to handle lossy DNG with Premiere you can buy fairly cheap slimRAW (49$) and convert your lossy DNG into lossless (there is Premiere compatibility check field), which will be read by Premiere. This is good workaround- you still have 100% quality RAW assets and they will be more compatible (for the price of being bigger).
I'm not sure if there is any free app which reads lossy DNG and properly converts them.
Last option- if you have Resolve then convert it to ProRes/DNxHR/Cineform and deliver this to client.