How do I get daily Konami rewards with minimum spoilers/effort?
Solution 1:
You just have to finish the prologue. So, about 1%. (This is my guess and solely based on my own experience. I'm currently at 3% completion, and the only significant plot related thing that happened was the prologue.)
It's plot heavy. It introduces several of the main characters you'll be facing through the entire game.
Yes. GZ saves are specific rewards. No matter when you do it you'll get the same rewards. The more you complete in GZ the more rewards you'll get.