yes, when I got my last visa there I didn't have proof of accommodation.. the guy there told me I needed to show proof of at least one week... luckily I had time to run to an Internet cafe and come back!
Oh no, I didn't realize this was a thing... I'm heading to Bali tomorrow to do this same thing... got one there 5 months ago, but I don't remember being asked that question
it depends what country your passport is from I think. I'm from the US, we get 30 days (but it's called a visa-exempt not a visa on arrival which might be the confusion)