How to find in documenation the QtQuick versions for a Qt version?
What business processes does one use to find the latest QtQuick version when upgrading to a new version of Qt? For example, I upgraded to Qt5.4 but my existing QML code imports QtQuick 2.3. But I just saw sample QML in this forum that imported QtQuick 2.4. (I looked in the release notes for Qt Quick http://doc.qt.io/qt-5/qtquick-releasenotes.html and it only discusses Qt5.1, i.e. its out of date.)
More generally, where is a discussion of backward compatibility for Qt Quick versions? I don't have any shipping code so that is not really pertinent to me, I just want to use the latest in hopes there are fixes that might help my problems.
Every new Qt release gets a new QtQuick version. It's a 1 to 1 mapping so far: Qt 5.x has QtQuick 2.x (so, Qt 5.4 has QtQuick 2.4). You can check that by opening the documentation for - for example - Rectangle or Item.
Regarding "backward compatibility" - there is no such thing in QtQuick. It is more like "forward compatibility", really.
Here is - rougly - how it works: when you include QtQuick 2.0 (I intentionally use the oldest available), Qt will create it using the available QtQuick version (2.4 in your case), but it will only give you the features that were available in 2.0. So, while you can't use never features without bumping the version number, you are still, automatically, benefitting from all the bug fixes.
This system is quite useful: when you do not need features from Qt 5.1+, you can just include the lowest number that suits you - and it will work on all those Qt versions (so you can ship with different Qt versions on different platforms).
On the other hand, if you include QtQuick 2.4, it will not run with Qt 5.3.