I'm developing an application with an underscore ("_") present in the app's name. Let's suppose "tes_t" is the name. In a search containing only "tes", will "test_t" be in the result? Does underscores affect in some way application indexing?

Is it ok to attach a html (only html and css, without js) file containing a short quickstart of the application? I already have a html for other purposes and it fits very well for reviewer to better undestand the application.

Is it true that Apple may reject a app simply because it is redirecting to another app? I mean something as simple as Facebook and Messenger, no information send just opening another app when user clicks on "Go to this another app". I was told this may cause a rejection due to a Apple policy and it is required to ask permission for Apple to do this. I think this is a bit strange, because it is not present in guidelines anywhere. The closest thing i found was about extensions.