If you are eager to try out those reward codes, but can't wait for The Talos Principle to be released (which is only 3 days away, but hey!), you can download The Talos Principle Public Test for free and try your codes there right now:

http://store.steampowered.com/app/330710

The latest update for The Talos Principle Public Test now allows you to redeem rewards codes from Sigils of Elohim. Note that you will need to get those codes from the latest version of Sigils of Elohim (updated a few hours ago). When a code is redeemed in the Public Test, it is not "expended", but will still be useable in the full game as well - as long as you redeem it on the same Steam account.