I replaced the all favicons in theme folder
oc-content/themes/veronika/images/favicons

But it doesn't show the custom favicon.

 And also doesn't display any icon when added a URL to homepage.

I already cleared the cache, and replaced all favicon with the required size.

You must upload favicons with same names as there are originally. Clear cache after that.

Yes, i added the same size, same name and in same folder still it doesn't load.

@abhkhan
What is your url and what favicon should be shown?

realfavicongenerator.net/favicon_checker?protocol=https&site=www.oyo.com.pk#.WseeF8uxU0M