You’re totally fine, forums and social media are made for the discussion and dissemination of information. Keep asking questions and keep on learning.

RCS stands for Rich Communications Suite. Its a standard developed by google to make texting more feature rich like dedicated messaging apps like WhatsApp or Telegram. Pretty much any stock android app uses it these days. If you want to know more here’s a pretty good explanation of it. https://www.androidcentral.com/what-rcs-and-why-it-important-android

You could have answered them in the time it took you to write that comment.

Just… why? It’s like you want to be an asshole.