Answer 1

It depends on the browser, since by default JS does not have a defined layout with respect to memory management (as far as I know)

Here you can review the specification:
https://www.ecma-international.org/ecma-262/8.0/index.html#sec-memory-model

Here is another very good article on the subject. I think this can help you a lot:

https://blog.sessionstack.com/how-javascript-works-memory-management-how-to-handle-4-common-memory-leaks-3f28b94cfbec