Availability of an application/synthetic monitor is not part of the RUM data, so it can't be queried from the RUM API.
You can get it from the Metrics API.
You can check the metric keys in the metric explorer. For the Availability of a browser monitor you can use builtin:synthetic.browser.availability.location.total
we are pulling availability details using metrics API, just wanted to know if RUM API provides the same details as well. Can you share the document link which provides explanation on user session, useraction table column details. User session returns multiple columns in response like apdexcategory, errorcount, duration, etc. i want to know details about the response fields/columns