Number of Logo that a CH can ask in one contest

Hello,

I'm sorry if this one has been posted before, I just couldn't find one.
My doubt is, Is it possible for a CH to held a logo design contest and he ask three logos in one contest? He doesn't explain that the contest would end with selecting gold, silver, and bronze winner, only 1 winner instead.

Thanks guys

I think I remember reading that the CH can "buy" other designs as well.