Thanks a lot brother, your answer did help and now copy paste is working in mobile on my website. Although there is now a custom CSS file also which we need to add to increase text size in editor, otherwise we get a warning in console.
Secondly, there are some other changes as well, since I want to remove image: link and image: advanced tab but they are not getting removed after these changes (and prior to these changes I was able to remove them). Apart from this issue, everything went well. Thank you so much again. :)