no, after you use the code you can't use it again.
proven by the fact that i opened a character in an another server and tried to use the code again and it didn't work.

Eu server is just another server but for eu so it's the same.

i slept in the afternoon so i can't sleep now lol

it's * because there is like 4 events. if there was a reset at evening ( start - 3 = reset) it would defeat the purpose of going to eu server, it will still be late

we can but we also can do it more early and let us play through all the events, there is no point in making it more late if you can make it more early. btw the first day is the longest (road to lv 29 - 30 )
getting it more early means more stamina and more chance to get to higher level ( we don't want people to be stuck at low lv because they failed at the first day to sleep late)