Could you let me know how and from where can i disable the this interest thing as i do not want the interest to be added automatically to my account balance without my consent. This will really help me and i can use this site with ease.

You can go to the profile tab, click the blue "disable lottery and interest" button, and then check the "disable interest" box.
I'm curious, can I ask why you'd want to do this? I'd love to hear your reasoning.