I would change the username to CrystalM00n
If you had my account for a day, what would you do?

Nothing much, changing other profiles wouldn't enjoy me, better stick in my life, my profile. There's enough to do and worry about.
But wait there's one thing: I could ask what people do in case they had access to my account for a limited time.

I would resign a bunch of games against comp easy and make you start all over again.
lol... my favorite reply thus far. Although these days I seem to be doing just that pretty well myself, without anyone's help. Take a look at my rapid rating for the past month or so.
As for the closing my account stuff... I knew that would come up sooner or later - or rather, I knew it would come sooner rather than later. But now that we have that out of the way, what are some ideas that involve keeping my account accessible?

I would...write a few forum troll posts permanently damaging your reputation as a troll on this website. I would also openly admit I was a girl.

I will play with Computer Impossible only.
I would have no problem with that. My rating probably wouldn't change.

The all day I will play normal standard blitz like they are 3 checks!
Well... at least that's better than playing normal chess like it's King of the Hill.
Or is it? I'm not so sure, now that I think about it. I guess it would depend on how you play KotH.
For 24 hours, you and only you are able to log on to my account, and do anything you want with it. After that time expires you will no longer have access to it. What would you do with my account?