So, after trying to flash kernels and images with fastboot I got the same problem as it was described early with K4. I can load fastboot mode, I can load diags mode, but I can't load main mode. MgfTool also doesn't work. Fastboot also can't help me to get into main mode using this commands:
fastboot setvar bootmode main
I checked everything before flashing, and I'm sure that I choose correct files.
May be we have the wrong kernel image?
I had 4.1.0 before. And I had succesfull experience when I flashed main image using dd command through ssh. I didn't flash kernel and diags images and at that time everything was fine.