I know this reply is way too late to help Rakshith, but it may help someone else. The type of alcohol to use for cleaning is 99% isopropyl alcohol. It can be a little hard to find, but a good pharmacy or drugstore should carry it. If not, it can be found online, although the shipping maybe a little expensive. 70% isopropyl won't work well because there's too much water in it. 91% might work, but 99% is the best.

I'm obviously a little late to this party, and I assume the OP has determined the answer to his questions by now, but I'll post this for anyone else who stumbles across it in the future. Neither the markings nor the color of your mid-2012 MacBook Pro USB ports matter. They are 3.0 ports, which you can check on using System Profiler. However, connecting a 2.0 device will configure them as 2.0 ports and connecting a 3.0 device using a 2.0 cable will do the same. Use the link below to read all the details. Definitive answers about Apple USB ports and troubleshooting can be found here - https://support.apple.com/en-us/HT201163