Yeap, that's what the demo is for. If you don't like the game - that's alright, you dont lose anything because demo build is free. But if you would like to continue in the full build - your save files would work just fine. In some cases I may need to fix some small stuff, but it would take about 5 mins for me.
And as far as I know Boosty has problems with paypal so I'm not sure about that, sorry :(