App Configuration Navigate to the GWM SDK's App Configuration page. Provide the following information:
Set App Visibility to Private. This setting is appropriate for testing and development purposes, and is the appropriate choice for these walkthroughs. Choose Public only if you're ready for your add-on to be used by the general public.
Warning: Check that your App Visibility setting is correct before saving. You can't change the App Visibility once it has been set. You must make a new Google Cloud project to set a different App Visibility. Set Installation Settings to Admin Only install if you want to restrict the installation to domain administrators.
Under App Integration, select Classroom add-on. You're prompted for the secure Attachment Setup URI; this is the URL that you expect to be loaded when a user opens your add-on. For the purposes of this walkthrough, this should be https:///addon-discovery.
this option is not found even if the SDK is of latest version, google project tyoe is web application, therefore i dont understand why there is no such option
See my comment for general advice but my best guess is that you don't have access to the Classroom add-on application type.
Classroom add-ons are in a private developer preview, so you must currently apply in order to build one. See the introductory documentation https://developers.google.com/classroom/add-ons#timeline