I've installed 10_33399 version and when I start a game, there are two issues:
1. I can't choose Demo level
2. When starting first level (Drone Creation), in the starting cell into which you are dropped down, after pressing the button on the right of the cell, the door at the lower right is raised up, but I can't get out of the cell in any way. I tried cutting through or hitting the floor, wall, etc. Nothing. I'm stuck inside the cell.

What do I do to get out of the cell, or even try the Demo level?

That did it, thank you. Yes, most console games would say something related to 'down', never 'off'. My mistake for ignoring something I don't understand.

Now about the difficulty of this game... Really. I guess I'll have to up ny reflexes with mouse pointing.

Hehe, yeah it's a bit of a stretch with the wording. I played with controller but when I looked at the default keyboard controls it was simply your standard WASD scheme, so basically the down key.

About the difficulty... It didn't take me very long to figure out that my reflexes would never be good enough to get anywhere with this game. Since I couldn't find a trainer that worked with this game version, I resorted to editing stuff on the source code level. You know, (almost) god mode, infinite ammo.. the only thing that could kill me was platforms, walls or saw spiders squashing me. I still have the edited DLL, in case you're not against cheating and want to make things way easier for yourself ;D