Real Chess is a well-featured chess implementation: play a friend on the same device or the computer at four difficulty levels, with 2D and 3D board views and both standard 8x8 and compact 6x6 boards.
The 6x6 option is genuinely interesting for beginners — a smaller board means fewer pieces and shorter games, which makes tactical patterns much easier to see.
Four, from level 1 (green, easiest) to level 4 (red, strongest).
A compact variant with fewer pieces and shorter games — useful for practising tactics, since patterns are much easier to spot on a smaller board.
Yes — two-player mode on the same device, alongside the AI opponents.