@7056
"using chess engines is unreliable" ++ The chess engine is reliable to calculate, but not to evaluate. To evaluate the 7-men endgame table base is reliable: draw / win / loss. The engine just serves to calculate until the 7-men endgame table base.
"a programme that stores every possible move in a huge database" ++ You cannot store every legal move: you will end up with 10^44 positions and that is too much. However, you can store only the relevant positions: 10^17.
"detects which sequence of moves leads to a checkmate" ++ No, weakly solving Chess does not lead to checkmate, it leads to a 7-men endgame table base draw or to a prior 3-fold repetition.
"we don't know which is a forced win..." ++ We know Chess is a draw.
@7055
"If both these players play perfect chess. Then why do all have different chess ratings"
++ The rating reflects the results of all games they ever played.
"And what about these guys with higher chess ratings" ++ These earned their ratings years ago, when more errors were made and it was easier to gain rating and earn GM titles.
"How do you play perfect chess and be lower rated then all these ICCF players"
++ Because it is now so difficult to gain rating or earn grandmaster titles, as many play perfect chess and the many draws lose rating that offsets the gain of the few wins.