Hey glad to hear you enjoyed it!
1. Yes.
2. Yes, as you unlock more friends and items, you will gain access to more and more areas.
3. I am aiming for the end of next year for release. The price will be $15, and my estimate at the moment is the game will feature 10 to 15 hours of gameplay. If I have time I will be able to add more content.
4. At the moment I'm not taking any puzzle ideas, and the only testing we are doing is internally and with alpha testers from the Kickstarter project.