So far I use Premiere Elements 11. Is this programm compatible with mp4 4K?
In the internet I saw a hint, that this is not true for PE 14, but may be for PE 13.
What about PE 11, PE 15?
I used 13 for two years with a Panasonic LX100 shooting 4K. I upgraded to 15 last fall and use it with a Panasonic GX8. I think it works very well with Panasonic MP4 4K footage. I've even mixed 4K and 1080p footage in a project!
The nature of 4K is that files are large. It will take a relatively strong computer to work with 4K footage.