Hello! Thank you very much for your interest. To answer your questions:
1: You can use any of the export output generated by the app for any of your projects, either personal or commercial. You don't have to credit us for it. Right now there's no specific sentences in the EULA that stated this, but there's no sentences that is saying against it either. We'll add more specifics in the future to the license but the general rule is something like what previously stated.
2 & 3: Actually, there's too much to count; you can try the free version of the app to find out yourself! You can find the download link in the itch.io store page, or if you're using the itch.io desktop app you can install the option marked as 'Demo'. The functionality that is reserved for the paid version also shows up in the free version, with clear 'Pro' markings on them.
4: You can contact us via other means such as our Twitter DMs or e-mail us at hello[at]ar14.works
Thank you very much!