"Before time" is an oxymoron.
As is the term 'virtual reality'. Peculiarities in the English language doesn't necessitate nonexistance.
Dimensions do not exist at all in the universe. They do not bend or terminate at the edge of the perceived universe. They are CONCEPTS for the mind and nothing else.
That's not entirely true. While there aren't great arcs in the sky that define the cosmic coordinate system, the universe still has properties that restrict our freedom when it comes to modelling space. For instance, the universe is demonstratably not two-dimensional, so we cannot use 2D polar coordinates (for instance). Whatever coordinate system we use, it has to encompass
all dimensions our universe exists in or could potentially exist in.
So if the universe is, or could be, in
n dimenstions, then whichever coordinate system we use must also have
n dimensions.
And these dimensions are not immutable: for instance, once you have formulated Einstein's field equations under them, you find that large masses and velocities will warp them in peculiar ways.
Likewise, dimensions do have a natural terminus: space ends at the end of the universe, by definition. Thus, any spacial dimensions must also end (how can you have length in nothingness?). Moreover, the same applies to time: there is a natural terminus where time ends (how can you time the timeless?).
The question concerning time is merely one of asking, "What was before anything was?" - Merely an irrational and illogical question the same as asking, "What is bigger than the biggest Possible?" - What was Earlier than the Earliest possible?
Ah, no, you are equivocating: "What was before time?" is not necessarily the same as "What was earlier than the earliest?". If we rewind the universe, we appear to reach a natural t = 0 scenario: the Big Bang. Now,
at t = 0, at the moment just prior to the Big Bang itself, the universe was in a certain state.
Now, there must have been a state such that the universe was without time, and a state where the universe
had time (i.e., our t = 0). The timeless state is the answer to the question 'What was before time?".
You just need to iron out the language a bit.