The rears can be bled just like the front, there is no difference. People will debate about the order of brake bleeding, but they all can be bled.

If the pedal feels more mushy or you have to push it down further, then yes, try bleeding the brakes, even if you didn't open the lines, it's likely the problem.

Bleeding is basically opening the brake lines to release any air that is trapped in the lines. You "bleed" fluid out getting any air out with it.