Sharepoint - How can I view a list of applications added by AppRegNew.aspx?

To look up registration information for an add-in that you have registered, go to http://<SharePointWebsite>/_layouts/15/AppInv.aspx.

To see a list of registered add-in principals (permissions), go to: http://<SharePointWebsite> /_layouts/15/AppPrincipals.aspx.

The second endpoint gives you the App Name and App Identifier (of all the apps) you've used while registering . You can consider this OOB approach if you just want to view a simple list of apps. For more detail, @Unnie's answer should be valid.

Taken from https://msdn.microsoft.com/en-us/library/office/jj687469.aspx

App registration using /_layouts/15/AppRegNew.aspx or through powershell is done for Remote/Provider Hosted Add-in.

You can install SharePoint Client Browser . Once you install and open your site inside it , you can see App Instances section which will show you all the apps installed in the web. Now once you select the app, from the details on the right hand pane you can find details. From the details if the AppWebFullUrl is null or blank then it is a Remote hosted App , for SP hosted apps App Web will be created.

Also you can do the same using code.

using (ClientContext context = new ClientContext("http://weburl/"))
            {
                Web web = context.Web;
                web.Context.Load(web);
                web.Context.ExecuteQuery();

                // Get all Add-ins installed on the web
                var addInInstance = AppCatalog.GetAppInstances(context, web);
                addInInstance.Context.Load(addInInstance);
                addInInstance.Context.ExecuteQuery();

                foreach (var appInstance in addInInstance)
                {

                    //Check whether it is Remote hosted Add-in
                    if (string.IsNullOrEmpty(appInstance.AppWebFullUrl))
                    {
                        Console.WriteLine("This is a remote hosted add-in");
                        // You can now get all the information about your appInstance object
                        Console.WriteLine("Add-in Title: " + appInstance.Title);
                        Console.WriteLine("Status: " + appInstance.Status);
                        Console.WriteLine("Start Page: " + appInstance.StartPage);
                        Console.WriteLine("Add-in Id: " + appInstance.Id);
                    }
                }
            }