Because this query could be interpreted in a few different ways, could you clarify what you're looking for? Are you interested in:
Help with a specific error or a missing file (like "part5") during the download or extraction process?
An overview of the features, updates, and system requirements included in the 2020 R2 SP1 release?
part5.rar , which appears to be a specific segment of a multi-part archive for the software.
Steps for extracting multi-part RAR files and installing this specific version of the AVEVA System Platform?