I saw answers here and here regarding this topic, but they're for version 2 beta (as far as I know we should bootstrap a module, not a component now; also I didn't find bootstrap
function in the docs for version 4).
I also read an article which points to an interesting comment in the source on GitHub. The most interesting part is
For this reason, Angular creates exactly one global platform object which stores all shared services, and each angular application injector has the platform injector as its parent.
Finnally, my questions are: What is the best pattern for inter-apps communication on the same browser page? How can we ensure some order of bootstrap for the different apps?