Asking for a friend.
Inside lemmy, yes. Pops up as a message.
Phone notifications would depend on your client. Voyager provides notifications for replies, but I’m not sure about others.
Depending on your instance, you may be able to get email notifications as well.
Top level comments, yes.
It reproduces how reddit works. Or used to work because over there nowadays I sometimes randomly (unpredictably) get notifications for lower-level comments too, which isn’t an entirely useless feature, but very much looks like “trying to increase engagement”.
Do you mean push notifications or in app notifications? Check your settings. By default you should at least have the in app one. If you don’t use an app you will also find a notification that you got replies too
