Where are the details on how to interact with the U.I. for Mass Effect?

I'm playing ME-Legendary (PC,casual). I'm at Eden colony. Ran across a dead body. Center Top of Screen says I should "Investigate". I've checked under my bed. There are no Geth hiding there. I've checked inside my cat's mouth. He hasn't eaten any of the characters. I can't find any instructions ANYWHERE as to HOW I'm supposed to "investigate"  this dead body. So...
1). HOW do I "investigate" the dead badly laying at my feet? What keyboard commands do I use?
2). Where are the instructions that detail HOW you're supposed to interact with the game? All I've been able to find is a Hot Key chart with over 50 Hot Keys that I assume I'll have to memorize.
3). Previously aboard NORMANDY I saw a pair of light blue parentheses appear on characters. I assumed that this means I should (or can if I choose) talk to that character. But how do I initiate the convo? Walking up to them doesn't do it. It just results in a Craig Ferguson style awkward pause that never ends. Is there a Hot Key I'm supposed to use to initiate the convo? If so WHERE is that fact covered?
 
The hundreds of videos on YouTube are of no help at all. NONE of them go into the particulars of the Mass Effect U.I.. All they cover are strategies for how to get to a particular point in the game, and various strategies on how to gain XP and the like.
WHERE ARE THE INSTRUCTIONS FOR HOW TO USE THE U.I. ON THIS WONDERFUL BEASTY?
 
Lastly - Isn't there any way to pause this game when "nature calls"? Or do most people just play with a bucket under the keyboard? And if there IS a way to pause - WHERE IS THAT LITTLE DETAIL EXPLAINED?
 
Sincerely;
Another Brain Dead N00b.