Flash Builder Help | ActionScript Compiler 2.0 Backward Compatibility | Everything about Flash | Scoop.it
From helpx.adobe.com - October 1, 2012 5:03 AM

This document describes the known backward compatibility issues between ActionScript Compiler 2.0 (ASC 2.0) and the legacy compiler. The document also includes features that are no longer available in ASC 2.0 and deprecated features that are no longer supported.