How I can save\load states, exit game, fullscreen toggle etc. via gamepad? What I must write in config?
What platform are you on? PC? a console? If PC, I would recommend using the input configuration tool in Retroarch-Phoenix (Settings > Input; those options are in found in the ‘misc’ section)
My platform is a Raspbian (Debian-based system on Raspberry Pi). And another problem is a RetroArch totally ignore my USB keyboard, but USB gamepad work correctly.
In that case, I assume you’re not using Retroarch-Phoenix? If not, you might be best served by using it on another machine to write the cfg entries and then copy them over. It’s not super-complicated to write them by hand, but it would be easier than muddling through it.
I’m not sure why it would be ignoring your keyboard 
I’m find the problem of a keyboard, it’s a passive USB hub which I’m use and which does not provide power both keyboard and two gamepads. And I’m find the problem with binding, cuz I try to use input_exit_emulator instead of input_exit_emulator_btn. Thanks.
No problem. I’m glad you got it figured out 