I hope my post didn't add to that confusion - but in case it did, my advice would be:
You can install Moodle2.4 on Ubuntu10.04. However, the only reason for doing this is if you already have the server set up on 10.04 with lots of other software on it that would make it difficult to upgrade. In that case, if everything is working and stable, why change (assuming you have kept all the security fixes etc. upto date!)?
You should use the latest LTS release whenever practical, as this will have the most upto date software packages, security fixes and the longest support time into the future.
In either case, you should ideally be using the Ubuntu Server packages rather than the desktop ones - although, in truth, although I would put anything going out on the web onto a proper server install, my own development system is in a XAMP environment on my laptop, and I use Mint for that rather than Ubuntu
Also bear in mind that if you are using Linux as your server OS, there are other alternatives besides Ubuntu, although this is probably not the right place to get into a comparison of them :D
To return to your point though Visvanath, I think that a number of the documents do need this kind of tidying up, but I understand this is an ongoing process. It seems to stem from the practice of rolling the docs over into the new version as a bulk action (as the majority of docs won't change between point versions) and then having to find the issues that need editing. As I don't have a practical alternative to this option though, I'm not in a position to (nor do I wish to!) criticise it - the whole of moodle seems to change so quickly in response to the wishes and demands of the community that keeping up with and tracking changes in documentation like this must be a Hurculean task! But perhaps that could be made slightly simpler when refering to external software like in this example, byt refering to 'the latest stable release' or something similar rather than having to ammend version numbers when other external software is refered to