Hi,
S32G SW packages are provided under the "Automotive Software Package Manager", available under the S32G2 product page (link: S32G2 Safe and Secure Vehicle Network Processor | NXP Semiconductors) inside the "Software" section.
Once you select the option, you will be redirected to another page where you can select the platform and either choose one of the available bundles or create your own. Since this will require approval from the NXP team, your bundle will be available to download once this happens. This can be delayed from 1 to 2 days.
For DDR validation, there are some tests already available inside Config Tools (bundled inside S32 Design Studio), which is used to verify the DDR parameters. For this, you should require both the "Real-Time Drivers (RTD)" and the "S32G development package". The latter should be provided inside S32 Design Studio, it just needs to be installed. More information on regards of the package installation is provided under the following link:
S32DS Extensions & Updates: Explanation and How To... - NXP Community
Please, let us know.