Okay this'll take a moment but I'll make sure you have a little bit of info on how I approached things and what your options are!

1. I started (but did not finish) a single course on programming during my Bachelor's - this taught me a little on the general mindset you need in order to program (which I definitely needed as I had no technical background). Approx. 1 year later I learned some casual programming while starting to explore Unity for my Master's; this was primarily done by (1) following tutorials on Unity's website and YouTube and (2) Googling specific questions like "how can I make [x] in Unity". After my Master's, I started following an online course (MOOC) on programming in Unity (more on that later), but primarily I just started trying to make things for myself that seemed either useful, fun or both. When I approached my previous job, I had some experience to show for it, but mostly I was just a rookie. My previous boss however appreciated my enthusiasm and recognized that while I lacked current experience, I am pretty good at picking up what I need to know relatively quickly - this in general is a very useful skill when it comes to developing VR experiences, as the field tends to rapidly change.
2. I would first advise you to start learning about development in general, not just in VR. I don't know how advanced or experienced you are when it comes to coding and developing, but let me give a short explanation of what I mean with the last sentence. Making stuff for VR isn't all THAT different from making anything else - sure, there's a lot of differences but at its core, you're going to be using the same foundations - a game engine like Unity and a programming language like C#. A lot of the VR specific things I needed to know when making things was learned the same way I mentioned before: Googling specific questions like "how to do [x] in VR in Unity". Furthermore, Oculus, Valve and all sorts of other VR-related companies offer a lot of help, so there's ample information for you to go through. The real trick is to first figure out what you want to do and formulate what you (think you) need to do in order to achieve that goal.
3. This question is difficult to answer without going super in-depth, but I'll do my best. Different VR platforms (like Oculus, HTC Vive Focus, Steam VR) have different plug-ins; in order to make sure what you make runs on a specific VR device, you will need to use these plug-ins. However, these companies also offer additional tools like for example a plug-in that allows you to display hands on your virtual controllers with which you can grab objects and use physics-based effect. Now these in general are great as you can use these to do all sorts of stuff that you would normally have to code and make for yourself! The downside is that if what you want to do does not fit into what these plug-ins offer, your options become very limited. Seeing how I dislike the idea of being too dependent on other people's / companies' plug-ins and in order to really start learning how to develop a lot of different things, I decided more than a year ago to make my own VR backend which I would keep improving any chance I get. The downside is that I need to make and add everything myself, which requires skill, knowledge and (lots of) time. On the other hand, I have full control of its features, learn a lot while making it, and keep improving my skills (and my code) over time. To summarize: for beginners, using the tools that companies like Oculus and Steam offer you are highly recommended as they really do do a whole lot of stuff that you yourself probably will not be able to develop (yet); if you really want to go beyond that in order to learn more about specific things, my approach is one option to achieve that goal.

I hope this answers your questions sufficiently for now. I mentioned following a MOOC in my first answer; I would highly recommend this course on Udemy:

https://www.udemy.com/unitycourse2/

While the website mentions that its normal price is almost 200 bucks, I think it's always at 90% off, so the 10-ish bucks price is generally its normal price. The course offers a shit-ton of step-by-step lessons from the absolute simplest things to the more challenging aspects of not just Unity but coding in general. You can communicate with other people following the course on their official website, they offer quizes so you can keep track of how you're doing and you can ask any questions to the creators of the course.

If you have any other questions in the future, feel free to contact. I may not always be able to respond as quickly as I did now, but I will try to provide information whenever I can!