I think the answer here is to be found in the glory of God. The catechism says that "Man's chief end is to glorify God and enjoy Him forever." That would sound silly if God were a mere man, or even someone as petty as the Greek or Norse gods. But if you take the God of the Bible, Who knows everything, is all-powerful, is all-good, and all-wise, then it seems quite fitting that He should get glory. Indeed, the glory of God is the greatest good possible.
So God created man able to change, and fallible, in order for Himself to get more glory. How does that happen? Through various attributes of God that show up in greater relief through His plan of redemption. Think about these attributes of God, and how redemption highlights them: holiness, wrath, justice, mercy, love, and grace.
You're quite correct that it "had to be clear for God while creating us that we will turn against him and eat the apple." Creation, Fall, and Redemption was not Plan B, but Plan A. God created a world where he knew man would turn against Him; but He also had mind a world where there could be only one way of salvation - a way that would bring God immense glory.
The word "cruel" cannot be applied to God. The fact is, we were the ones who messed up, not God. God gave Adam as good a shot at paradise as anyone could want, but he sinned; and because we were covenantally represented in him, we all sinned with him. The Bible clearly teaches that we are responsible for our own sins. Therefore, a sinner going to hell is uninteresting. That's what we should expect, just as uniform straight-line motion tends to stay in uniform straight-line motion. What's incredibly wonderful, and astounding, is that God saves anyone, rather like the outside force acting on that uniform straight-line motion. Why should He do that? He could let us all go to hell, and it would be what we deserve. Instead, He saves some purely out of His own goodness.