Are sub-practices located under specific practices expected during CMMI Appraisals (e.g. SAM SP2.4 there are seven sub-practices. Are Appraisers expecting seven artifacts or artifacts that prove all seven?
The CMMI defines Goals as required, Practices as expected, and everything else as information. So no, you do not need to produce evidence at the sub-practice level - only at the Specific Practice level.
However, as "informative material," sub-practices embody the intention of the authors of the CMMI and further describes and clarifies the meaning of the practice.
It's good to read them and understand what the authors meant by each practice - but it doesn't mean you need to produce evidence for every one.