I installed Ruby and Rails couple of months ago, and I do not remember if i used Homebrew or RVM or rbenv.
Presently I have all the three installed on my Mac. I did not touch the system installed Ruby.
Is there anything I need to worry about with these three things present on my system? Is there a chance that they may mess up my perfectly working Ruby and Rails environment?
Which one should I keep or can I keep all three?
If I need to remove any or all, can anyone also help me in removing everything, RVM, rbenv, Homebrew, Ruby and Rails and make a clean installation?
You will likely want to keep Homebrew and either RVM or rbenv.
Once you decide which Ruby version manager you would like to use (rbenv or RVM) then follow the instructions to uninstall one of them, either brew uninstall rbenv assuming you installed rbenv with Homebrew, or rvm implode.
From there you should be good if you didn't touch the system Ruby.