Changed pads on all 4 sides yesterday. Afterwards the rear were spongy. Some questions.

1) Can air get in the lines if I didn’t take any lines loose? I did take the calipers out of the rubber boots and grease them.

2) If I bleed them on the rear, can I just bleed from one side or do both sides have to be done?

3) Is the fill reservoir on the handlebars or is there also a separate one under the plastic for the rear?

I ran out of light but im going to check and make sure the inside pads aren’t hung up on the caliper this afternoon. Its a Grizzly 550.