Aces and Kings is a demanding two-deck solitaire. Eight foundations sit in the middle: four build upward from ace to king, and four build downward from king to ace, regardless of suit. Cards come from tableau piles and two reserve stacks, and only the top of each is available.
The double direction is what makes it hard. A card that would be perfect on an ascending foundation is often the one you need to keep for a descending one, so almost every move is a decision rather than an obvious play.
Two decks, eight foundations: four built upward from aces and four downward from kings, ignoring suit. Cards come from the tableau and two reserve piles, top card only, and you win by clearing all 104.
Considerably. Building in both directions at once means most cards have two possible destinations and only one right one.
Yes — tap a card and then its destination. Nothing to install.