After reporting the copied designs their support staff mailed me and said "They are not copied. Freelancer has taken the images and modified it.
Which one can do to make a logo."
They really don't care about stock imagery rules and almost every design is copied. As per their Customer Success Specialist(don't want to ruin his name) copying images from stock image and modify it with logo is legal and can be use to sell on their website by their freelance users. This site is supporting illegal actions and supporting copiers. It's a fraud for employers who are posting projects and contests on their websites.