Thanks guys. Although the phone has upset me a lot of times ever since I bought it, our community have never ever. I mean, this is not the first time I had problems, but everytime I always received advices with enthusiasm from a lot of people of the community, even our device has been abandoned. You guys have my respect. I myself lost the enthusiasm long ago.

So I finally managed to fix it. It turned out the battery was a little loose: not loose enough to be unable to boot (can still flash, use rescueOS), but when it came to boot maemo, it shutdown halfway. So what I did was: cut a piece a paper, and shimed to the right edge. Voila.

The lesson is: If flashing doesn't solve the problem, you might want to consider the battery.