Ill try and answer 4.

The difference between being able to draw line of sight on a target(LoS) and not being able to is usually dependant on 1 square.

If you want your characters to shoot down on a target they have to be on the "rim" of the elevation to be able to target. Putting even 1 space between you and the rim blocks all LoS to lower elevated targets.

Usually a character standing on elevation 2 shooting down at a target on elevation 1 has LoS, even if that character is adjacent to a friendly or opposing character. In the same manner, the character on the lower elevation CAN fire back, or target that character. There is no penalty for damage when firing from or to elevation.(think of this as they are higher, they can see over everything)

The only time this does not work is when the character on the elevated rim is adjacent to the charater on the lower elevation because normal spaces adjacent to elevated ones are not considered adjacent for targeting(unless you have Leap/Climb or similar power) or placing purposes(when you carry a character you cannot set the carrier down on elevated and the target on lower and vice versa)

Things to note- Colossals can be targeted regardless of elevation because they are so "tall" you can see them about 99% of the time, and they can see you(eat shit Ziran). Remember to check the level of elevation you are currently on, as the ramp/ladder/stairs usually has a number next to it telling you which level you are advancing to(its a red number on most maps)

I hope that helps your question! Also I seriously laughed on number 7 because I nearly broke poor Jewel because I did not know I was susposed to turn her from the bottom of the dial and probably had the same line of dialouge haha.