But every time mr. blue box touch "scream1" canvas the sound was playing, even with "once" condition.
<img src="http://i.imgur.com/V25YY.jpg" border="0" />
so I created something that works, but it's stupid, don't you think so?
<img src="http://i.imgur.com/bf0mG.jpg" border="0" />
It's working good, but I don't think is good to use solution like that, because there is probably other, better solution with events.
Nothing wrong with your solution, but if you want a different one, here's what I suggest: Create a global numeric variable with an initial value of zero. Let's call it "screamed." In your event, you'll need to check for On Collision AND whether global variable 'screamed' is zero. Your actions will then be to play the sound file and to set global variable 'screamed' to 1. This will guarantee that the sound file won't be played again even if the sprites collide.
2. Now quite complex one. I create game for 1024x768 resolution, but many people have other monitor proportions like 16:9, 16:10. I send preview exe to two guys with 16:9 monitor and everyhing is working, but graphic was streched horizontaly, and I really don't know what to do with this. Help.
I don't really see that as being a big problem. Many professional casual games are set at 1024x768 resolution. There is some minor horizontal stretching when the games play at full screen, but that never bothered me. If you're making your game for the general public, this resolution will be playable on all but the most ancient PCs.
3. In one place there is huge fps drop:
<img src="http://i.imgur.com/XGsB7.jpg" border="0" />
censored due to brutall stuff
I know the project is very graphic "heavy" (an will be only more), but fps drop only in one place, when mr. blue box jump (1) to another place (2)?
I'm not seeing any huge FPS drop, although I do have a pretty good rig.
If I were you, I'd optimize the use of graphics to save on VRAM. Many people who play 2D games don't have the computing power to play 3D games. Replacing your background Sprites with Tiled Backgrounds is good advice. Even better, you can break up the repeating parts of your backgrounds and stretch them across your layout. Stretching a tiled background will not deform it the way it does to a Sprite. Instead, it will cause the image to repeat across the stretched area.
Your graphics and sounds are excellent, by the way. I wish you the best of luck with your project.