I have an old alpha version R11 of the game, I assume the 0.50b is newer and I should just download that one?The correct version for the story is 0.50a or 0.50b.
You can find 0.50b HERE
Is the link at the bottom of that post.
Yarizo level 4+ are not yet implemented, the events that need level 4 are already there, but you can't increase the level yet.
If you use the Cheat Item you can activate the Event Test Mode which is going to show you a list of events every time you do something that triggers one. So you can pick the level 4 events from that list.