I've completed kq8 several times now and I know, that kq8 is buggy as hell, but this one is new for me.
I can't give a horn to unicorn. Unicorn is just inactive, I can't even talk to him.

Should I start the game from the beginning? =)

Serious!!! I've got the original cd of this game from when it was released, but I decided to buy this game again on gog assuming that these bugs would've been addressed. at least I didn't make a start, I would've been royally pissed off if I got far in the game only to find I couldn't complete it again. What a bummer, such a good game too.