Very though provoking, Erkka. There's a lot to chew on and discuss here. Thanks to your skill at writing I can see that your thoughts work in a similar way to mine, with some exceptions of course.
I think you are really on to something with the analogy to computers and the idea of greater complexity of calculations eventually reaching a sentinent or self-aware state. I think our human brains are in fact such complex systems. The physical world in and around us seem to follow rules which even the brightest minds have not yet fully discerned and never will. The atoms we are made of are mostly empty space but yet here we are as gravity holds us on the planet and holds us in orbit around a star at exactly the best distance and so on. There seems to be an ascending system inherent in the makeup of the universe. Consider that the planet Jupiter is just barely short enough on mass to become a brown dwarf star. It seems that when something reaches enough mass, enough gravity, enough complexity, enough of “X”, it reaches the next phase.
On the subject of free will, I think a good chunk of evidence for it's existence is that fact that we have made such a mess of our world and of the time we have had here. There are murders, assaults, wars, greed, envy, jealousy, etc. This may sound very off-topic but consider that nature has no garbage. Nature left to itself is a perfect system in which there is no waste. Everything is recycled and used for something else, eventually. The fact that we have free will is best evidenced by the fact that we in many cases choose to go against the natural resulting in harm and waste to ourselves, others and the nature around us. There are many other cases I can make for free will, but this is a good starting point. The more you study nature the more you see how very perfect it is at it's inner core. With all this said, I feel that we would be remiss to forget that we are not only physical but also spiritual entities and the two are intertwined. I know this may spark a good deal of debate, but hey, It's what I believe and perceive after my 40+ years of comtemplation.
On the God thoughts you expressed, I feel the need to express an alternate viewpoint. You visioned that , “In its Christian from the question is: "OK, so after you die, you are taken to God, who then will evaluate your actions. If you have done bad things, you go to Hell, but if you have done good things, you get to Heaven.” I think this is partly accurate but it leaves something critical out of the equation. We have ALL done bad things, so God sends everyone to hell? No, he provided a solution for us through the sacrifice of Jesus Christ to die in our place, taking on the punishment we deserved.
You continued, “Then, at the same time, we also teach that The God is omnipotent, has created everything, and knows everything, and sees the future. Logically, doesn't this then mean, that God already knows what you are going to do and to choose? That you can't choose to do something which The God didn't already plan for you.” I think you have it right up to where you said that you can't choose to do something God didn't already plan. This is where free will comes in. Remember we have engaged in war over our human history. That is one example of going against nature, evidence of free will. Successful organisms preserve their race and their numbers, not exterminate and stifle itself. It points to other supernatural influences at work. A battle if you will, outside our normal perception.
You also said, “And what kind of God is that, who first creates a bunch of bad people and a bunch of good people, and then pretends that the actions and decisions of the said persons warrants them eternal time in Hell or Heaven?” I really do see where you're coming from in a logical standpoint, but God never created anything bad, ever. “Badness” is a cancer we are all born with, which affects even physical reality as we know and perceive it. We are born into it. It's source was supernatural and born of a small seed of jealousy.