Can I use a (gcc) compiler version different from what is listed in the Release Notes?

The short answer is that only the platforms listed in the Release Notes are supported.

A platform is defined by a CPU architecture, an operating system and its version, and a compiler version. For example, i86Linux2.6gcc4.1.1 means Linux 2.6 on an Intel processor with version 4.1.1of the gcc compiler.

Can I compile with gcc version 4.2.4 instead? Will it still work? Will it be supported?

We have only tested the platforms listed in the Release Notes. We have seen situations where using untested platforms has resulted in hard-to-find problems which were ultimately caused by compiler differences.

To guarantee our software on your platform, we want to make sure your platform is on our list of supported platforms. Some customers use our standard libraries on slight variations of the platforms and do take a risk. Others have contracted with us to test their platform and add it to our list of supported platforms. Please contact your account manager for more information on this. 

Coming back to the example of mixing gcc 4.1.1 libraries with gcc 4.2.4; as long as the problem can be duplicated with gcc 4.1.1, it is supported. For example, if there is a bug in our product that is unrelated to the compiler version, it is supported.