The insert() is attempting to insert the all of the fields of the entire JSON, and the collection does not have all of those fields. The error that you received, sort of points that out, " field name prefixed with symbol ‘$’ ". The insert() function is trying to insert the fields $version and $etag .
The object passed to the insert() function must be exactly what needs to be inserted, You will need to extract the fields that you want from the JSON and create the appropriate object to user for the insert() . Refer to the insert() API for details.