Not quite. "Push technology" is sort of an all-encompassing term for server-to-client updates whereas webhooks pertain specifically to HTTP callbacks. An example of a webhook would be GitHub making a POST request to some URL (set by the user) whenever new commits are made to a repo. Push technology might take the form of webhooks, long polling, WebSockets etc.
Webhooks are traditional HTTP requests so I don't believe HTTP/2 changes anything. The ability to differentiate notifications depends on the service / API you're integrating with.
Webhooks are traditional HTTP requests so I don't believe HTTP/2 changes anything. The ability to differentiate notifications depends on the service / API you're integrating with.