1998 Prius ABS On and brakes doesnt work

Hi guys

I had this car since 3 years i guess, but yesterday when i turned it on it was beeping and i put it in reverse, then behold the brakes didnt work as usually, but when i pressed very hard it stopped slowly.

I though brakes were stuff up, but i moved car up to big parking space and was keep going backward and forward, suddenly the beep stopped and the brakes worked as it should.

But now today i though i will do the same thing, but the beep doesn't goes off and brakes doesn't work at the same time.

When i turned on car, i can hear some sounds like tak tak below bonets.

Any one know why brakes doesn't work.
I have attached two photos as well, that's what it shows on screen..

Any help would be appreciated, i have a manual in English, which is very small and doesn't have anything related to these signs.

Thanks