Mount Batur

Yes, guided treks are standard practice (and generally required) for the sunrise climb.

Moderately — around 2 hours of steady uphill walking in the dark, manageable for most reasonably fit travelers.

Widely considered yes — views over the caldera lake and, on clear days, as far as Mount Agung, are a genuine highlight.

A headlamp/flashlight (usually provided by the tour), warm layers (it's cold before dawn), and sturdy shoes.

Yes, Kintamani's viewpoints offer a much easier way to see the volcano and lake without the trek.