I don't undestand what you mean by version 4 and 7 but it looks like you are using the latest version of Magick.NET. I made a lot of changes in version 7.0.0.0101. Below is an answer to all your questions:
- The Font, FillColor settings are now set with the Settings property of MagickImage.
- The Gamma method has been renamed to GammaCorrect.
- GetPixels is indeed the new method that you should use.
- MagickResourceLimitErrorException was removed by accident and will be included in the next version of Magick.NET.