As of today , does intune app protection policies applies only to the off the shelve microsoft apps only. I only MS apps whem i try to configure app protection policy. Eg if i want to add webex to app protection is is feasible? How can i apply app protection to any third party app.
To use Intune App Protection policies the app needs to have the Intune SDK integrated which not alot of third party apps have. See following link for an overview of how this integration works: https://docs.microsoft.com/en-us/intune/app-sdk
What you should look for is If the app you want to protect supports AppConfig which is an open standard for any EMM. Using AppConfig you can enable SSO, DLP, Encryption etc. You can find out more about AppConfig here and also check if the vendor for the app you want to configure supports it: https://www.appconfig.org