Giants - All the questions and hopefully all the answers

There's been quite some discussion on giants recently, that I think it might be worth exploring all the issues related to it. I would try to centralise all the questions in this thread, and hope someone kind enough would help with some answers. Please note that this is started in the interest of all so all helpful information is appreciated.

1. What is a giant betta? Or what qualifies as a giant betta? If there's a size vs age guidance, so much better.

2. Any distinguishing features that separate a giant from a normal betta (beside size)? Please be clear in your description.

3. When breeding giants, what do you expect? E.g. faster growth compared to normal sized betta? How to tell any piece is a giant, since we all know that only some of the fry turn out to be giants. Again, we need to be specific, as most of the fry would turn out larger than normal betta.

Let's use plakats as a starting point, before we get confused talking about HMs, veiltails, etc.

Any more questions that you want to ask to help you learn and appreciate giant betta? Otherwise, let's start with these questions first, and contribute all that you have seen, heard or know here.