Solved it finally using the chart I created. Posting it here for the benefit of others. I was following the A connection colour code for the Patch Panel and Wall socket!
Needless to say, I have checked the availability of Ethernet connectivity at all floors, out of those all RJ45 sockets. So the connectivity now looks like this:
DSL twisted cable pair in --> DSL Modem + Router --> Patch Panel --> Cat5 to Wall Socket --> Wall Socket to laptop (last mile).
Most of the work done was physical in nature at the Patch Panel and following the same connectivity sequence, correctly connecting the coloured twisted pairs inside the Wall Sockets.