Yes two Imperials do not block adjacency to square 2

Really? The Imps don't block line of sight or anything? ****.

So then could he make a ranged attack?

There are so many different cases in this thread, so it's hard to say. If you talk about the second example with three rebels and one imperial and a wall between the imperial and right-side rebel, the two left-side rebels are adjacent to the imperial, and the third rebel on the other side of the wall is distance 2 from the imperial, but both have line of sight to each other due to sharing a corner (thus allowing ranged attack or melee attack with reach). (Ends of walls, doors and blocking terrain spaces do not extend beyond the corner of a space.)

What about this situation:

[ ][R]

_____

[i1][i2]

So lets assume R is a Rebel with reach, can he attack I2? They can draw line of site to each other from the corner of that wall, but there is Imp1 blocking the space he would technically draw his reach accuracy through? I understand you don't need accuracy for melee, but do you need to be able to draw your set number of reach spaces through a clear path or can the spaces be blocked by other figures? And if R was doing a ranged attack, would it cost 1 or 2 accuracy?

Had this problem come up last night with my newer group and I honestly couldn't remember. We hadn't played in so long I probably learned this stuff before but have since forgotten it.

It's fine. Reach requires that the target is within 2 spaces and the attacker has line of sight to the target.

1) I2 is within 2 spaces of R.

2) R has line of sight to I2.

(Due to sharing a corner and you can draw line of sight through the target space.)

R and I2 are distance 2 from each other, so a ranged attack would require 2 accuracy.

In the last example, if there was a figure in the top left square next to the rebel, it wouldn't matter, right?

It wouldn't. I2 is still within 2 spaces and R has line of sight to I2 due to sharing a corner.

(The rules for Reach are also in the handy reference cards.)