Back in the days when fliers could do ranged attacks against figures they were based with, and grounded figues could do ranged attacks against fliers they were based with, did things get a bit confusing?

I imagine people had to be very specific about their attacks while based. For instance, if a flier was attacking a non-flier who had combat reflexes, did they have to be sure to declare that they were making a ranged attack?

Would a non-flier who was based with a flier that had Energy Shield/Deflection sometimes say: "Hmmm, I could use Ranged Combat Expert on you, but you've got that ES/D.... Ok, I'll make this a close combat attack in order to play it safe."

If someone forgot to declare what kind of attack it was and just rolled the dice, what was the default assumption?

Also, could doing an Energy Explosion against a character you were based with potentially give you splash damage?

I always make sure to declare what type of attack I am doing.
If my opponent is not clear, I usually ask for clarification.

And yes, you could get hurt (still can if you are a "sharpshooter" I guess) by your own EE.

And "back in the day" it made fliers with Combat Reflexes real angry.

Yep.

I saw that fairly often, actually - +2 is not trivial.

Close combat action.

Sure could. This can still happen if you use the Fuel Tank special object.

This rules change totally nerfed the original zombie Spider-Man

Could a flier with CR declare that he was turning off "flight" before ending his turn?

Yes you did have to be specific but I don't think it was more complicated. I kind of miss it. The only positive thing that came out of it was that fliers with combat reflexes are not useless.

Yes you could...except that all canceled powers return upon the completion of your turn. Sorta like turning off stealth so your team mate could perplex you or PC your attack. Stealth automatically came back on at the end of your turn.

I don't think is optional.

Symbols are not optional, no.
Nowadays, you can choose to cancel the abilities granted by the symbols... but since the symbols do not change there's rarely any point to do so.