Some answers:

1.  No, not using the RQM URL Utility.  Instead of using the RQM URL Utility, consider writing your own HTTP client or using the Poster/HTTPRequester Firefox plug-ins to receive the raw XML response content.  

Note: Your example uses a HTTP GET request .

2. In your example, you are using a test case result (executionresult resource).  The executionresult resource ID does not increment but rather a new executionresult resource is created during each test case execution.  Likewise, new test case execution record (executionworkitem resource) can be created and associated it to a test case.  Finally, you can GET the test case execution record(s) (executionworkitem resource(s)) that are associated to a specific test case (testcase resource) using a fields filter (see https://jazz.net/products/rational-quality-manager/api-doc-4.0.6/schemas/qm_xsd/elements/executionworkitem.html#a31 and https://jazz.net/wiki/bin/view/Main/RqmApi#fields).

Note: Your example uses a HTTP GET request .

3. No, this is not supported using the RQM URL Utility.  Note, the RQM URL Utility is just a simple HTTP client that can be executed from the command line.  See https://jazz.net/wiki/bin/view/Main/RQMTestAutomationAdapterAPI for writing test automation tools.