Sorry for the delay, and thanks for the feedback! I would like to try to figure out what's going on with your game so that if I need to roll out a fix, I can do that.
For mega evolutions --- you should have an option from the dex to mega evolve when you reach mastery (catching 30 of the same species). There should be three buttons (aside from close) --- Buddy, Party, and Mega Evolve (100 coins).
Once you trigger the mega evolution, it should start a 60 second period of automatically spinning, and both the slot and the environment have some animations that only happen while a mega is active.
If you are not seeing the mega evolution button, or if it isn't populating after mastery, I will have to look in to that, just let me know.
To access the ruins, try clicking the unown pokedex entry, and quickly tapping the icon 3X. Let me know if it works for you. Also, try visiting pallet town again and quickly tapping on the town name at the top --- curious to know if that works for you, as well.