I have had just one DMT smoking experience and it was the most intense experience of my life. Since then, I've twice had a similar DMT like experience during sleep. It felt very different from regular dreams wherein I wasn't aware that I was dreaming. These two dreams however seemed different. It was vivid and detailed and I was aware of the fact that I was somewhere else although my awareness didn't seem to have much control of whatever was happening. I was simply observing.

In the first dream, I saw a couple of different frames, in one I was petting a few dogs at my house(no one in my family are particularly fond of dogs. I love them though), in the next I was having sex and the next I saw myself happily walking around in a room that somehow felt familiar and while walking I happened to look over at a mirror that was next to me and I saw myself as a much older version of myself.

A few days later I had a similar experience while sleeping. This time I was at a friend's place and I had taken some psychedelic and was tripping. I was seeing everything in slow motion and I was jokingly karate chopping a friend and I was so fascinated by how slow things were moving and how much control I had of my moves. I did a couple of backflips because of how light I felt. Like the scene in Spiderman where Peter Parker dodges punches in slow motion. I was also hallucinating. Later I saw a couple of colourful geometric shapes and then woke up from sleep.

I'm just curious. Would this have anything to do with parallel realities?

OK, there are parallel dimensions. True. But what just created that thought and therefore parallel dimensions as a fact and truth? The brain did through language. The language center of the brain contains autobiographical memory and the capacity for executive "ego functions" such as deliberate mind-wandering and conscious introspection of mental content. To know the fact of parallel dimensions would, I believe but am not sure, be impossible without conciousness that permits language. Therefore Parallel Dimensions and the Theory of Relativity only exist through the brain.
The brain creates its society. And the society creates the brain~~the latter is easy to discover, however the former is complex, deep, and goes into the metaphysical realm. Because if the brain creates its enviorionment that would imply that the brain has an inmense, godly power.
Strategy (a modus operandi of conciousness that uses deep atention for insight into the future, also created by the complex brain) advises to strike all things at their source to achieve an effective result. Well then, what is the source that permits the complex functions of the brain? Does its power have a source? If so, where and when is it?
So elusive is the unkown...

Let me provide an alternative viewpoint.

We can consider parallel realities from a spatial viewpoint - analogous to different places across one or more dimensional axes. While our scientific and mathematical understanding of dimensions and spaces is tied to language, our primitive spatial navigation abilities are nonverbal, analogous to similar abilities in animals and preverbal children. Therefore, the understanding of such phenomena does not require the dissective, analytical 'verbal' mind, and instead can happen in an 'analog' manner.

Also, the question of seniority can be raised between 'layers' of reality - is understanding emergent from physics, or is physics the representation of understanding.

My theory is that understanding, aka. Spirit is the fundamental nature of existence, and that the sense of space is at a very fundamental layer of the 'creation' of reality, more fundamental than language. In this I tentatively disagree with spiritual approaches where the 'Word' or 'Logos' is considered the fundamental nature of creative Spirit.

About the dreams... I also tend to have these sorts at times. Sometimes even weirder ones.