Yes, it does offer offline mode. I didn't have any plans to make it backwards compatible since 87% of all devices are running iOS 7+. If there turns out to be a large demand, I will definitely look into it.
I really like this idea and was willing to try it out but with this iOS7+ limitation I guess it's dead end for me. I think there are still many millions of pre iOS7 users out there that won't be able to try this app out. How hard is it to make it compatible with other iOS? The XCode compiler doesn't do this for you?
A lot of the features and frameworks used are for iOS7+. Hence it would be a major rewrite.