Absolutely. Android devices are dirt cheap, and ubiquitous in most of the world. It's an obvious choice for many based on that alone. There's also lots of families that aren't in Apple's ecosystem.
Flatfire
As far as I'm aware, Samsung or Amazon are the only other real app "marketplaces". Most developers using Fdroid otherwise rely on donations or patreon for active development, depending on the nature of the app
When people refer to a particular piece of development aoftware as closed or open source, they are referring to the license/availability of that software's code. You can use proprietary software to produce open source code, which is the case with Android Studio. The code that makes up Android Studio is not open source, but your own work made within it can be.
In general, "open source" is a broad term that just means "can I see the code that made this?". There are differing degrees of open source software as well. The MIT license, for example, opens up code to some modification/re-use but protects some libraries. Something like a BSD or GPL license is far less restrictive, usually allowing free modification and use of the code. Android Studio falls under the Apache license, one of the more restrictive licenses that still applies copyright, and may employ proprietary libraries that cannot be modified or copied for use. Again, this ultimately isn't likely to affect your own work or projects, but it does mean there's less transparency about the tools you are using to make it.
I apologise if this is overwhelming, but the distinction is important, and I think that as a beginner it makes sense to start with where there is the most documentation and ease of entry. Once done, it's definitely easier to move towards projects that more closely align with FOSS philosophies.
Android Studio is just the work environment for code and app development. You could continue on to publish all your code/work as an open source application through whichever means you choose during or after the fact.
Imo that's fine. It's also still the best tool for learning since it's the most widely supported one, and contains the greatest amount of documentation for working with android development. It costs nothing to use, and doesn't lock you into any kind of ecosystem you can't later migrate from.
Android Studio is the primary toolkit for developing native android apps. If you have no background in programming, there are some more visual tools like Budibase (open source) or Softr (closed source), but you are likely to run into difficulty getting them to apply logic the way you'd like.
If you're a tinkerer, then honestly I'd look into learning more about Android Studio and Kotlin, the language most used these days for app development on Android.
Also worth noting is their history as an IP mill. Dead By Daylight is a surprise hit amongst many a licensed deal to produce games that would nearly qualify as shovelware in most cases over the last 20+ years. DbD gives them some independence, but they're still largely a "studio for hire" by anyone who needs them.
I firmly believe this Quest exclusivity junk is stifling VR in a way that sets it back quite a lot. There's a lot of interesting ideas, but the closed ecosystem that Meta/Facebook has crafted is detrimental overall. It limits the peripherals, the fidelity, and it doesn't even have the kind of competition something like the old console wars did. It's just dumb.
Not arbitrarily. I've just had difficulty launching deb and AppImage packages from within Wayland after downloading them. I have to explicitly navigate to Dolphin and launch them. I know what I downloaded, I want to be able to run it from Firefox's download menu.
Same, I couldn't find an open issue for this anywhere. Now if they wanna fix the ability to launch executables from Firefox under wayland I'd appreciate that.
Hey there, I'm not sure I understand what you mean by "first activated". In general, you activate a SIM card, not a phone. This would be associated with your current phone plan, not the device itself. Your carrier would be able to provide that info. If you're referring to when your phone was first purchased/turned on, then most folks tend to add their Google account during setup, which might be why there's a suggestion to check your Google account to see when the device was added.
The IMEI is potentially useful as it's a device identifier, but generally doesn't matter to anyone except your carrier.