Firstly this was the correct place to ask the question.
Secondly I am sorry that the documentation was not clear and you were not able to understand the page both Drigax and I pointed you to
Thirdly the PG you just included in Mesh adds bounding boxes - #60 by ranwei-001 does not help us to answer your problem.
My issue in answering your questions is unfortunately they are not simple enough for me to understand what you want. As I have said before you must break down your issues into much smaller ones. Putting your full project into the playground is not doing that.