Hey there, happy to answer these.
1. Tutorial is coming, but the basics: Photograph monster girls, submit those photos to the monpedia if they are doing the action it asks for, increase familiarity levels with the girls (not fully implmented yet), raise your research level by taking good photos. We will be adding in a lot more on the main loop soon, the game is in very early development atm.
2. Could you send your hardware details to me please? Like what is inside your computer. You can also try capping your frame rate. Version 013 which we just released should add a lot more optimizations to the game. But it is also physically saving a photograph to your computer when you take photos, so if you're on a old and slow HDD that could cause it.
3. Nope, you wont get a steam key from itch. Itch and Steam are two different store fronts, you wouldn't expect an Itch key for purchasing the game on Steam, not sure why people expect something like this.
Let me know if you have any other questions.