What counts as uncovered?

A card with nothing overlapping it. In TriPeaks each card is held down by the two below it; in Golf, by the one directly beneath it in its column.

Not at all. Only rank matters, in either direction.

Why can I not play an Ace on a King?

You can in TriPeaks, where the chain wraps. You cannot in Golf, where Ace and King are the two ends of the line.

Can I go back to the stock after it runs out?

No. The stock passes once, which is why clearing the table with cards to spare is the real skill.

How long does a game take?

Three to five minutes. These are the fastest games on the site.

How to Play TriPeaks Solitaire — Rules Explained

How to Play TriPeaks and Golf SolitaireLearn TriPeaks and Golf: play any uncovered card one rank above or below the turned-up card, and chain long runs to clear the board.