As MB PRO does have internal storage, this is used analogue to "use USB first" and named "use internal version" not to misguide users that it might need an additional USB thumb drive or alike.
Current version is 3.3. When "use latest version" is selected (default) you will get the 3.3 in the state it has evolved right now on every boot. Once we freeze 3.3 and step over to 3.4 the frozen 3.3 will be selectable in the list, to allow you to stick to it. As we regularily do updates and fixes it will not be handy to have all ever made version for download (would be more than 100). Versions we do a freeze on are usually well tested and reported doing fine by the forum response.
