Yes, and this is quite easy to achieve - you just need a lot of practice, and it is in the vocabulary that you mostly think about (otherwise, you will constantly jump to your native language, where you know this word). And as soon as there is a solid base, after a very busy interval (not necessarily a long one, the main thing is active involvement - you just need to speak) for some time "by inertia" you think in this language without thinking. As soon as you stumble, you immediately jump back, although after a while you learn to come back.
For this it took me about six months of intense communication with a native English speaker, so that later I could catch myself thinking that I was thinking in English all evening, without touching Russian at all. At the very beginning, it worked for a short time, you quickly get confused, and you get tired in principle.
So yes, it is possible.
I can't say about changes on an ongoing basis, but sometimes, when I arrange a five-hour marathon of English literature, or watch films, TV shows in English all day, in the evening I think only on it)
Yes. When you live in a foreign environment for a long time and constantly speak another language, thoughts slowly rebuild. The language, of course, must be at a good level)
Well, for example 19 years old and height 161 cm