Definitely the Twister. It's really one of the only roller coasters that I can make without it being ridiculously over-extreme, and I love the whooshing sound it makes. The Giga is also a favorite.
I think, if you go to the autosave/ directory, it will have previous autosaves. Just go to the one with the date/time that you are looking for, then save it normally to save you the trouble of digging through the autosave/ directory.
I am unable to open the openrct2. When I try to, my computer says that it can not run on my computer. (for reference, it's a Iview Maximus II, a touchscreen laptop)