I have a url which when runs gives an error. This url is of full copy sandbox. In order to resolve the issue, I need to know the vf page name, however I cannot identify the same by looking at the link. Please suggest what is the vf page name in the below url
This is a force.com URL, not a salesforce.com URL. This means this is a page on a Force.com Site.
Try going to Setup > Develop > Sites
In there, you should find your Site Label and Site URL. Click on your Site Label and you'll see a list of all of the VF pages associated with that site, your page(s) should be in there. That should get you on the right track to finding it.
Based on the structure of that link, I would guess in addition to being a Force.com site, a UrlRewriter class is being used to mask the name of the VF page. When you look at the the Force.com Site, look for the UrlRewriter field and if popluated, look at the class to help you determine what page is being used.