ad 1) You can use it only inside SPPB Module
ad 2) I don't associate it with ours. Ask the person who originally did the site.
ad 3) We used custom Social Icons module there, no FA icons but SVG.
As I said before those are just links to Social Media, not Social Share links.
ad 5) Use Icons Group addon - it allows you to add many FA icons and put custom links (URL).
ad 4 & 6 ) As I said before it's not possible to have YT and Instragram Social Share.
Currently, some social media platforms (such as Instagram or Tik Tok or YouTube) restrict their API and therefore it isn’t possible to share content across an endpoint through an application outside their environment.