In so much as we are unable to measure the size of the universe .

It's difficult to imagine it, but space is something we live in. And the Universe appears to be able to make space bigger - but there's no "outside".

If there were another Big Bang, and it was outside of our Universe, and we couldn't detect it, we still might predict it. With don't currently have a theory of everything. But some forms of String Theory suggest that there might be Universes that have no contact with ours. So we wouldn't know of other Universe per se, but we might have a good story that suggests that they exist. At the moment our ignorance isn't good enough to know this one way or another.

"Once you can accept the universe as matter expanding into nothing that is something, wearing stripes with plaid comes easy." - Einstein

In theory, the Big Bang created this universe and everything in it so there shouldn't be another Big Bang. We'd be straying into multiverse territory to consider others.

It's not really an empty void, but yes. Time, space and everything else was created at that moment. It's only a theory but it's the one that most scientists agree on. Just like things explode outwards the force of the BB is still causing the universe to expand...in theory..

there are theories of multiple universes the most prevalent being the bubble universe which equates creation with a sea of bubbles each bubble being a universe unto itself. who knows????? it will never be resolved in our time. might as well come up with one of your own. you may be the one to get it right but i'm not sure what the prize is, maybe immortality.