Man was created in time, and if God revealed the whole truth outside of time - this would imply man has perfect knowledge upon his creation, correct? And therefore why do *anything*, right? Why not just make man perfect, instead of with free will, etc.? I think because He's a jealous God and wants people to willingly worship Him.
So He makes us, give us free will, let's us totally mess up, right? But He knew this, which is why Christ was *always* a part of the game plan. Christ exists before man's creation - so it's not that God changed anything. He just reveals Christ at a certain time. Why then? Who knows?
But the fundamental idea of belief in "Christ" was always a part of the plan. Maybe it wasn't called out specifically as "Christ", but the idea that, "Hey, believe in God, believe that God gives life, have faith...heck, even kill your own son and trust that God will raise him from the dead..." was always a part of the deal. The only thing that really changed was that after Christ, He said, "Just believe in *this* guy...", but before, during and after Christ the only real requirement for a relationship with God was faith, and faith alone.
The animal sacrifice and all that...they were actions demonstrating faith, and had no power in and of themselves.
I'm not sure if thiseven comes close to answering your question - I'm writing between reading boring resumes.. - but I think also your question perhaps can not be answered ever toyour satisfcation in this life. You are essentially trying to establish some operating parameters that your incredibly finite brain can comprehend, and then apply these parameters to a God you call infinite...it's like bug spit on the sun - you can't impact something so large with something so small...you can't understand and infinite God with yor finite understanding.
Is that a cop out? No...it's just reality. And the other reality is the God reveals to you what you *need* to know. You can think about the rest, try to figure it out (and fail...)...but He *has* revealed enough for you to understand what He *wants* you to understand, enough for you to have the relationship with Him that He wants, and that's about it. The rest is thought games...which I think He also encourages.
Why do we only get such a small picture? I don't know...maybe becuse the angels were given much more...more knowledge, more power..and they realyl screed the pooch with it, didn't they?