I don’t really care, the number of rolls in a game might be too much or too little either way.

Because I don’t know what their max roll might be and it achieves them something, they gain knowledge that something is impossible for them.

I really love Mouse Guards simple skill progression where skills advance when you have succeeded AND failed with them enough times.

Why wouldn’t China do exactly the same mistake in some point?

As European I would advice against the trust that the strong economic ties would keep totalitarians in check.

This is hard one because most of the one shots are just awful as they rarely include any guidance to how to run them in short of time. At least every one shot should include a guidance of how and which parts to leave out when time is running out.

So the best ones are usually systems designed for one shots without separate scenarios but assuming you are asking about those the most palatable one has been DnD 5e adventure Sarah of the Yellowcrest Manor from Candlekeep mysteries. The middle part can be pretty much skipped if the time is limited, there is at least some guidance on how to run it and the end dungeon is short and sweet.