Hello, 
I have a survey for my products which is public. Anyone can fill the survey questions. I am fetching those survey responses using Limesurvey API on the Front-end of the website to display under each product. I want to add some sort of moderation to survey responses before they go live on my website. Is it possible?

This is something you need to do on your end, after you got the responses via API. You need to build your own revision system before you display them on your website.

Limesurvey collects data as is. That's it.