Despite spending his half of the life in null void and already knowing that it's an alternate dimension, Kevin in the forge of creation said " I thought the universe is everything", when he seen other universes
That doesn't really mean anything.
Servantis while being in the nullvoid said "no one will be able to bring Ben Tennyson back, not in this universe or any other", suggesting that nullvoid is the part of the universe as an whole.
That is simply he calling the Nullvoid a universe, not that it is part of Ben's universe.
Also plumbers who were created to maintain peace in the universe also maintains the nullvoid, proving it further.
From 9:53.
Of course they do, they use it as a prison to toss beings there from their universe, they need to have it as a responsibility because of it.
There is no evidence that null void is not in the same universe/timeline. There can be more than one spacetime continuum in a timeline. Best example is Dragonball.
https://vsbattles.fandom.com/wiki/Zen'ō.
The wonky way DB has things working is, like all wonky things, exceptions, not the norm. Spacetime continuum and timeline are synonyms, you can't just use another verse to claim otherwise here because that's ridiculous. Nullvoid is in another dimension, dimension in this context means "reality of unknown size" as fiction often has it, thereby it isn't in the same universe, its page in the Ben 10 wiki even quickly links to a source stating it's not in the same timeline.
Not to mention each timelines are branches off from primetimeline must also have their own nullvoid if they use it to imprison criminals. Just like this alternate future timeline, which confirms that nullvoid despite being seprate spacetime continuum (sub timelines) is a part of all encompassing timeline.
Who cares, the Nullvoid could be branching off timelines in its own as universes do or already have them all. You have no link for that last claim but it doesn't mean anything, if they all use it then all have one.
In dragonBall even universe 7 has shown to contain more than one spacetime continuum which is written on vs battle page clearly.
The reason for this is that Universe 7 by itself has already been shown to contain parallel space-time continuums within its globe, such as the Room of Spirit and Time, which is still affected by time travel; which proves that the new timelines can encompass other space-times as well, and thus the events in the Future Trunks Saga don't prove anything in the way of the universes being physically connected.
Also nullvoid has more better and good evidence to be separate spacetime continuum than of room of spirit and time in dragonBall. So ig it works. Also 2c universe/timeline is possible.
The evidence you use for this is beyond bad, and stop using example for other verses, your stuff needs to hold up on its own regardless of how nonsensical the rules are.
Also, Nullvoid (a said alternate dimension) was introduced in Ben 10 classic when the concept of multiverse wasn't yet introduced
This point is pathetic, it doesn't mean anything and when something doesn't mean anything you don't use it as a point,that builds up bias. It was a dimension of unknown size at the time.
and even after multiverse was introduced in the next series yet it was never said or specified that nullvoid exist outside of the universe, leaving no reason to assume so unless stated otherwise.
It is already known by the fact that it's another dimension, unless one were to assume it's a pocket dimension inside the universe, it doesn't matter.
All your arguments are very bad, people here not having been able to reply on their own on what's wrong with them is something to improve upon.
