I've been working on an idea that I'd like to implement ( I've written a paper on it) . The method that I've mentioned includes sending notifications to android users present in an area without specifically installing my app. First, is it possible? Second, I've looked into Firebase cloud messaging- I'm aware that it should be tethered to an app but is it necessary that the user has to download the app? Third, are there any other methods by which this type of push notifications can be sent? ( Based on location) Finally, I'm sorry if you feel I haven't put any effort I'm new to this. Thanks in advance.
Such a service is known as Cell Broadcast when talking about SMS/Text messaging.
There is nothing built in for it in Firebase Cloud Messaging. Even if there was, it would require an app that uses Firebase Cloud Messaging.