Earlier versions of Lightroom (5.7.1) are not uninstalled when new versions are installed (LR CC/LR 6). That's the way the Adobe installers work.
Yes, obviously, you now have both to use if you want. My recommendation is to not use LR CC/LR 6 to do "real" work until you are committed to doing all your work in LR 6/LR CC. Use LR 6/LR CC for learning and with test images. The reason for this is that some of your work in LR 6/LR CC cannot be transferred back to LR 5.7.1 if you decide to stop using LR 6/LR CC.
Hello Mr. Paige
thank you so much for quick response. Appreciate it.
However, i have seen that while starting Lightroom 6, it asked me to convert the catalogues into newer / updated format, to which i had said yes. Now the question is if i continue to use Lightroom 5.7 and update pictures, and then again Lightroom 6, is it the correct way? wil it corrupt?
No chance of corruption. THe problem you may find is that your LR 5.7.1 catalog will not match your LR 6 catalog.
This again is why I say that you should use Lightroom 5.7.1 for "real" work and Lightroom 6 for test images, until you reach a point where you are confident that you will switch to Lightroom 6. Then you can upgrade the LR 5.7.1 catalog to LR 6 (again) usinf File->Open Catalog in LR 6, and this new LR 6 will contain all of the "real" work you did in Lightroom 5.7.1.
Thank you so much, Appreciate it.