specify pom.xml in mvn command and mix goals of other project

Solution 1:

Just mvn --help would have answered the first question:

 mvn -f otherPomFile.xml

No. You can simple execute the phases for the current project you are in. You can give multiple phases like

mvn clean install site site:deploy

Solution 2:

For the first question, see khmarbaise's answer

If you want to build more than one maven project in one step, you must use modules.

In a multi-module project, if you call mvn install from the top project, all sub modules are built, unless you use the advanced reactor options (e.g. mvn install -pl util -am only builds the module 'util' and it's dependencies)