I don't use Android Studio, so I don't know how bad usability could be for something this simple, but as for debugging, have you tried using breakpoints instead?
If Android Studio has upgraded your project to something that earlier versions can't handle, can't you take a backup of your project from before that update, and use that instead?
But in general, I'd advise to accept that software changes, and get used to it. Getting stuck with an obsolete version is not really feasible in the long run.
You're only showing the directory layout of the source code. After building the project, is the DemoServlet.class file in the directory WEB-INF/classes/arjuncodes?
The JVM does indeed reclaim available memory automatically (as you observed, since your app never runs out of memory). Often it will only reclaim smaller amounts of memory than what calling gc() would reclaim (because smaller collections take less time and CPU), but sometimes it does indeed do a full GC.
I'm not aware of any switches that would aid in container environments, but maybe others have experience in this area.
I think that's unlikely. Kotlin is the go-to language in the Android world (where using Gradle is required), so most Android programmers know Kotlin much better than Groovy. But Kotlin use in the wider Java world is much less pronounced, so I don't think Groovy will be dropped.
Remember that jQuery UI -just like jQuery Mobile- is basically obsolete. You shouldn't use it for any new projects, and phase it out in existing projects (unless those are in maintenance mode, too).
My advice is always the same: work on something that YOU are interested in, not something that other people suggest you might do. That way it's much more likely that you will apply yourself, and try to do a good job of it. There must be things that you have long wanted to automate - why not combine what you want to see done with what you want to show off?
Java 1.4? No, most definitely not. Java 8 is barely acceptable these days, and Java 11 somewhat more so. But for a new project, start it on Java 17 if you can.
But your question is not clear. Just about everything is a project, so what, specifically, do you have, and what, specifically, is still missing that you need help with?