If you want to execute robot twice, you could pass -v BROWSER=EDGE or -v BROWSER=CHROME on the robot command line. This will make the variable ${BROWSER} available to your test suite.
You could also use -V and pass a variable file the suite should use. We use that in order to run our tests in different environments like QA or production, which needs different URLs, hostnames, or whatever is pertinent to a specific environment.
I'm not sure if that's the kind of thing you're looking for or not.
Craig