1. Does the fact you used the exact title, word for word, for this thread that I, a non physicist suggested, mean I am better at physics than you?
It makes you an excellent author and should consider professional title making.
2. Since the pre-big bang universe was something that existed in a state with no time, and it was only with the post big bang universe that time itself came into being, and if the universe does have an expatriation date, this will likely be the death of time. Though if it's true that energy cannot be destroyed, the universe will exist in some form. So I'm curious as to whether, when talking about the universe, terms like finite or infinite are even relevant?
That's an excellent question, and in short the answer is we don't know - but I can tell you what we *do* know! In fact an infinitely countless different possibilities here. We call the big bang the beginning of time, yes, i.e. it is the t = 0 event with respect to the lifetime of the universe. However this is given first of all the big bang theory is indeed a correct model, and there are studies which allow us to infer it (red shift of galaxies, a distributed temperature profile when looking into the celestial sphere, etc. which imply expansion, which then taken backwards in time implies contraction) Given this was an event which occurred (according to current estimates) 13.7 billion years ago, to infer something this major is difficult to say the least. There is the multiverse theory, for instance, which can then explain the existence of our universe *without* the need for the big bang. Point here being, to place the time measure for the universe relative to the life of the universe is itself on another theory. We can only hypothesise. Energy cannot be created nor destroyed, yet can be changed from one form to another in a *closed system*. Now that last part is very essential but often missed out. A closed system is where there is no energy exchange at the *boundary* of the system. Treating the universe as a thermodynamical system, is it closed or open? Does it have a boundary? These are open questions. So basically it is unknown if the first law of thermodynamics applies to the entire universe itself. Finite and infinite are mathematical constructions to describe quantities. They make sense in the mathematical structure, and given mathematics is the language of physics, it exists in that domain also. But it must be understood they are themselves not physical entities. Much of this question leaks into the "Philosophy of Science", so these parts escape the realm of science (my expertise) but I hope I have given you some sort of idea of where we are up to in terms of understanding the universe. A lot of open questions still left over!
3. People have theorised many ways the universe as we know it will end/die, the two most popular being the universe collapsing under the weight of it's own gravity (the big crunch) or having a finite mass to expand and then snapping back into itself like an elastic band. Providing either of these are realistic possibilities as far as our current knowledge goes, could this be one in a chain of a number of big bangs, the big bang that we're familiar with being simply one in a long line?
Assuming the former is true, it would lead to the conclusion of at least one big bang (provided the big bang model is correct). The latter would lead to a multitude of big bangs, but elastic objects are (contrary to the name) never truly elastic, there is energy loss, resulting in damped oscillations. So eventually after a number of big bangs there would be a cutoff point. The universe would be progressively smaller after each big bang. Now if the process is 100% elastic, then you'd have infinitely many big bangs and big crunches. So that means it *could* hold that this is just one of many in a long line!
4. What the fuck is up with people in planes ageing slower?
In a plane the effect would be minimal, but try orbiting a black hole, or travelling at close to light speed! The former is known as gravitational time dilation (general relativity), where a massive object causes space-time (yes, space and time are interconnected!) to curve. The mass of the object determines how much space-time curves (the more massive, the more curviness!) and time dilation occurs! So basically it's a way of saying, time is being stretched out (you are still travelling the same length in the path along the curve, but it's taking relatively "longer"). Now as for travelling close to the speed of light, then strange things happen. It is known as special relativity. Time dilates as a function of the high velocity, for reasons not entirely known (the universe is just weird!) A very neat explanation can be found here http://science.howstuffworks.com/science-vs-myth/everyday-myths/relativity10.htm