>>47232940>>Can a Kirlia/Gardevoir/Gallade be prominently good in strategy games?Sure.
>>Do the full moon affect the Ralts line in any way?I don't think so no. They don't learn the move moonlight nor do they seem to have any immediate connections to it besides the move "Moonblast" which a lot of fairies do.
>>What signifies a Kirlia has come of age?Probably some physical change like, you could see X Kirlia looks older than Y Kirlia. This would extend to Ralts, Gardevoir, and Gallade as well, I'm sure there are children Gardevoir and Gallade too.
>>Are Gardevoir banned from playing Chess?No. Considering Alakazam play chess and their future vision powers seem to be even stronger than Gardevoir and Kirlia. Though sure, you could ban them from playing chess, if you wanted to.
>>What role do they serve in nature?Like most Pokemon, we don't really know. I assume they protect things/pokemon and that's the Ralts' family's core identity?
>>How beneficial it is, for a Ralts growing up, showing love for it?Very? The same way that Ash's Pikachu is strong because of love and friendship a Ralts would be very strong for the same reasons. However, the dex mentions that its later evolutions (Kirlia & Gardevoir) grow strong from these bonds so it really could do more. Unfortunately their movepool and evolution methods do not back this up.
Ralts->Kirlia->Gardevoir should have been a friendship evolution like Lucario or Lopunny and they should have had a Special Psychic type Return...but this is really minor anyways so eh, whatever.