Thank you very much.
I will try more. If I correctly understand you, usbboot and fastboot is a single process in this case and despite of usbboot success ("sending image to target" message) and green LED etc. almost every time I try it, if fastboot commands (e.g. "fastboot boot ./recovery.img") failed on "waiting for device" message, than whole "usbboot" process is failed, too.
And one more question, is fastboot cable useless for now, until chip is fixed?
Thank you once more for your time. I'm sorry if my questions are too stupid.
Yes, you probably don't need fastboot cable for this procedure. And remember, there's no such thing as stupid questions..
Well, I take it back this is XDA and you'll get eaten alive if you ask something really silly.