[@Lucidnonsense]

[b]Are all species of Dimensional Long lived? orr can relatively short lived types exist as well?[/b]

Long lived and short lived types are allowed, yes. A reason why Jakquel is so, long lived is because he created the planet Flarin. He's as old as the place he created. 
Not all dimension species have to create a dimension or planet. They literally could create a plant, animal species, or anything else. Though they end up loosing at least one of their seven senses. 

[b]Did the dimensionals originate in our dimension? [/b]

Think of it this way. There was a spot in a box. That spot grew into a larger area and that black box expands into the universe. Now that little spot was a high energy that created the dimensionals. 
Now that spot that created the main dimensionals (which are around Jakquel's age) told them to make their own planets. In the end the dimensional's whir able to create different dimensions separating their planets from each other. 
Now all the dimensionals who were original are all protects between the portals of the dimensions on their planets. Though there are shorter lived dimensionals which are half human/other species. Which the original dimensionals are called Raspstones and their offspring are called jinx's.  

Now Jinx's live shorter and are half of some other creature. They do what their parents did. Usually loosing one of their seven senses if they create planets/dimensions/etc. 

Now if your character wanted to be a child of two dimensional parents it would be considered of the Magic generation. Or they are just considered Magic. Which Magic's tending to be just like their parents. Though they can be stronger and it's known they can die in very young ages or live for long periods of time. 

So, really if you want a longlived dimensional character...Create an original or a Magic. But if you don't want, a longlived one creates a Jinx.  



~ I hope, I answered your questions correctly.