The rules say that only the emulator deSmuME 0.9.11 can be used, why the newest one can`t be used? Also, can i use any date to make the speedrun?

You should post both of those questions in the Pokemon Diamond forum as they’ll get answered better there.

Though I can offer a little assumption into the emulator rule as I’ve dealt with DS games before, and it most cases that rule is because that version of deSmuME is the one that is closest to an actual DS in terms of performance.