Free Grimoire: Manastorm

They want you to have a fake FB profile, that's why

I'm not so sure, maybe the promotion will end at that time in case there's still some keys left. If I was you I would redeem the key as soon as possible.

That's the coupon expiration date. That's the last date you will still be able to lookup in the give away system what Steam key you received, when you follow the link, e-mailed to you.
Edit: because that's how https://woobox.com/skdrgz works.

Yep, I wonder if ppl actually can be bothered to read the fuckin rules

damn those ninjas coming in and not replying to getting the code ):