Voting system with viral effect

Hi

I need suggestion here, right now i want to create a contest for my blog, i mean the rule like this, i have a category on my blog, on each post of that category will add a vote button (only on post under that category), and on the end of the week we will choose the winner (which post will win based on vote)

What I am gonna ask is,
1. is there any vote plugin that can use for this kind of contest that hard to be cheat?
2. is it possible that every voter need to like a FB pages before they can vote?
3. have reset facility to reset the vote every week

thank you 🙂