Chess Grandmaster offers two things: normal games against a computer opponent, and a set of chess problems — positions where you must find a forced mate or a winning tactic in a set number of moves.
The problems are the more valuable half for improvement. Below expert level, most games are decided by tactics, and drilling positions where a tactic exists trains you to see them over the board.
Composed positions where a forced win — usually mate in a set number of moves — exists. Solving them trains the pattern recognition that decides most real games.
Tactics. Below expert level, most games are lost to a missed fork, pin or skewer rather than to an opening mistake, so drilling tactical positions improves results faster than studying theory.
Yes — tap to move. Nothing to install.