Toward the front of the clutch cover there's a vertical tube in the case with a big bolt in the bottom. There's also a bolt (plug?) in the front of the engine case. What are these for?

A machined oil channel between main case and cover based crank junction, they put a threaded bolt in it as technically you could want to clean it out for an oil blockage if one ever took place.

If you want to, and if you can prop the bike more upright, it's a way to drain the oil filter.

Also, the oil passage that leads to the port on the lower front is connected to the one facing downward. If someone wanted to connect an oil cooler or remote filter, they could block the connecting passage. Then oil would flow out the forward facing port, through the cooler/filter, then back in the downward facing port, into the stock oil filter cavity.