How does file verification work?

[mainrs]

Context

I am archiving my games on a NAS. I want to periodically re-download updates (if available) using lgogdownloader. I was trying to figure out how lgogdownloader checks for existing files and ensures that they are valid. I came to the following conclusions and wanted to ask if these are correct:

1. Existing files are only checked by name and size.
2. Downloaded files are checked once after download against the API's md5 hashsum.
3. Partially downloaded files are downloaded in chunks of a configurable size.
4. Resuming a download checks each chunk against its own md5 hashsum.

I am wondering where these md5 hashsums for the chunks come from, too.