Why would you want to downgrade to version 6.3 as that version you have is the latest at v2015.5.1 or v6.5.1 [ 1073342 ]?
If you are talking about the "Version: 6.1" listed after "Operating system: Windows 7" it is the Windows operating system version not Lightroom's. That is on the first line.
@BKKdon - Thanks for the quick reply and your tip.
I now realise I was referring to the old pre cc version number that was/is 6.3 - when in fact the CC version numbers are quite different... DUH! - I got totally confused by the two different version numbering systems.
Just for your knowledge.
LR 6 and the CC versions are exactly the same. Even the numbering is similar.
LR 6 has been updated from 6.0 through 6.5.1
LR CC/2015 has had the same update numbering as LR 6. It started out as 2015.0 and has had the same updates, because it IS the same program, through to 2015.5.1.