Solution: I installed a new (another) BIOS, using USB flash with BIOS and fn+r keys combination. 5 minutes deal. Now I have access. Also, old BIOS password and settings still there - good!
G580 after replacing BIOS battery laptop not starting. Webcam LED on, power LED on, I can hear HDD and fan. But black screen only. After 4-5 minutes laptop just turns off. Need help!