I replaced front pads and bled front brakes only should i blead all again ? The abs light comes on sometimes.

ABS equipped vehicles require addition attention when brakes are serviced. Refer to the service manual for your vehicle for the proper procedure.

It's possible that there is a bleeder directly on the ABS controller unit which needs to be bled as well. It's also possible that you need to use an OBD scanner during bleeding to "set" the system for bleeding.

Note that it can be difficult to fully bleed your system if air has gotten into the ABS modulator unless you have a pressure bleeder tool.

See additional info here:
http://www.aa1car.com/library/abs_bleeding.htm

No you're fine, ignore the light unless it stays on

Yes you should bleed all the fluid out of each wheel till you get new clear fluid, do it one whheel at a time.