Have you ever?

Fortunately no.
Have you ever won some race or competition ?

Yes, a Fireworks tutorial contest. It was a while ago though.

Have you ever done something very nice to a stranger, unplanned, just on impulse?

I think not.

Have you ever cheated in KS using Level editor?

Some time ago. While most of the cheating i did is by using "that" code, i used to sometimes search for the solution to a puzzle in the editor. Nowadays i only do that for trial and error puzzles, though.

Sometimes i also do things like adding "poorly" to a big "designed by {username}" screen, or replacing text in a sign thingy with bad grammar with "Me perfectly speaking English are", and of course that time when out of boredom i decided to implement a KS+ feature in Raicuparta's Some Room.

Have you ever signed up for a forum that has nothing you could contribute to at all?

Yes, I am doing it right now. 
Have you ever locked yourself somewhere and couldn't get out ?

Maybe! I remember my mom talking about one time she accidentally locked my sister in the car and had to call the cops; however, like most people her memory isn't perfect and that could have happened to me. It would have to be when both of us were real real little.

Have you ever caught yourself visualizing a music video set to the song you're listening to?

If I listen to music on the very threshold of sleep, it takes on strange properties, with instruments adopting personalities and sequences of notes corresponding to narrative implications. At the time it feels transcendental, but it's probably just stupid. Hopefully this response isn't too off-track from your question!

Have you ever had some kind of life-changing moment that later turned out to be a dud?

I don't think my life is full of radical life-changing moments, in both good and bad sense. It's pretty stereotyped but I'm not complaining.

Have you ever seen a falling star?

Yes, several times. The most memorable ones were when I was on a holiday in greece a few fell in a duration of 4 minutes.

Have you ever made something that you were sure was very good, and you only got bad opinions about it?

It happens to me every time I bake a rhubarb cake. I don't mind it, because make them the way I like.
Have you ever broken your leg or hand ?

No.

Have you ever played Antichamber?

That game where you can't even know something's there even if it's right in front of you? Played it for some time, then got stuck on one puzzle where you have to go through doors but need all the matter for the thing right after. I think i got past the point where you get the green gun.

Have you ever been hated on by some fans of something you shared your opinion on, which were like those PewDiePie fanboys?

Yes, some friends of my sister, anime fans, dislikes me for absolute no reason (I just said something ugly about some demons-hunting hipster whose name I don't remember).
Have you ever edited anything at Wikipedia ?

Yes, mainly the binding of isaac wiki.

Have you ever played an Atari game

YES! And the graphics were so much better than BF4. BF4 graphix sux

Have ever played super hexagon?

No, but I played Hexagon 2 quite a lot, which super hexagon is a sequel of. That lightbulb exploding when you won was quite an effect for those times. I was very astonished by it back then.

Have you ever been the leader and gave leadership to a team of at least 4 people (you excluded)?