Yes. Sure: the top of my head is 2.5 ft above my navel and my feet are 3.5 ft below my navel, therefore I am 2.5x3.5 = 8.75 sq ft tall. Right.
As already answered, there are several reasons to believe that the Universe might, right now, be of infinite size. The "theoretical" size of what Cosmologist call the "Observable Universe" depends on the model (the system of equations and assumptions) we use to calculate it. Often it is estimated to be about 46 billion lightyears in radius, meaning it has a diameter of 92-93 billion light years. But what is meant by "observable universe"? It means, crudely, that all of the stuff that was close enough to the stuff we are made out of for it to interact with our stuff. You may know that the Universe is expanding. This means we are slowly "losing touch" with some of the matter (the stuff, which includes light). RIGHT NOW (and we'll ignore what "now" means in Relativity Theory, just assume it has its common meaning) Stuff which is more than about 15 billion light years away from us is moving away from us at ever increasing speed. This stuff can NOT ever be seen by us; meaning there is no way it can influence us in any way. - its essentially not there as far as we are concerned. But at one time the Universe was much smaller. Some estimate it might have been a few meters in diameter, others think it started out smaller than an atom, but our Physics fails at the start of the Big Bang, so that remains an open question. Anyway, most of us believe that some of the stuff which was close enough to interact (at the speed of light) then has expanded out to about 46 billion light years. And yes, if you calcuate its "average expansion speed" you get 46 ÷ 14 = 3.3X the speed of light. But this expansion is not the stuff moving through space, but the actual expansion of space, so there is no limit on how fast this can be.
Two aspects to point out. 1. The Observable Universe isn't all observable. Things which are 46 billion light years away will never again be close enough to us for them to have any meaning for us. The OU contains all the stuff that we would have seen at one time, if we were present at the beginning. 2. A lot of Cosmology assumes that the Universe is isotropic and homogeneous. These assumptions mean that there is (on average) no special place in the Universe: it looks the same (on average) from anywhere. (There are good reasons for these assumptions, and there is some evidence that they are approximately true). What this means is for an alien living on a planet 14 billion light years (bly) from us, that it would look up at night and see a sky which was pretty similar to ours. (Different constellations, different galaxies, but the average 'structure' of the Universe would look the same.) This means the alien's OU would look about the same but include things that are NOT in our OU. So, we'd need to add that "extra" volume to the size of the ENTIRE universe. But there's no reason that another alien couldn't be on a planet 14 bly from the first (and 28 bly from us), and we'd add that volume too. And another could be at the edge of Alien 2's OU. Since homogenous means none of these aliens would be at a special point (the edge of a cliff or wall IS a special place) that we should continue to assume the universe goes on forever, even though the stuff that was ever close enough to us has only been able to "travel" to no more than ~46 bly from us, the stuff that we couldn't interact with at the start (or ever since) could be billions, trillions, and more, light years distant "now". But talking about stuff that we never did and never will interact with is like talking about the angels dancing on the head of a pin; you can have a multitude of different opinions about them, and we'll never be able to determine which, if any of them, is correct.
