How will old revisions, in cases where they would trigger edits if they were current, be displayed when viewed?

To clarify my motivation for this question: As I understand it, each post that is currently not valid CommonMark will be updated by one non-bumping edit (which I presume will be shown as having been performed by the Community bot), translating the latest revision of the post from the Stack Exchange's current Markdown dialect into CommonMark.

When an old (i.e., already non-current) version of a post, accessible through the post's revision history, contains Markdown that is incompatible with CommonMark, how will that version be rendered when a user accesses it? Will it still show the same HTML it once had?

And when diffs are viewed in the revision history--in the "inline" and "side-by-side" views--how will they appear? Will existing diffs (i.e., those between two successive revisions that already exist now) still render the same, no matter how old?

How will old revisions, in cases where they would trigger edits if they were current, be displayed when viewed?

To clarify my motivation for this question: As I understand it, each post that is currently not valid CommonMark will be updated by one non-bumping edit (which I presume will be shown as having been performed by the Community bot), translating the latest revision of the post from Stack Exchange's current Markdown dialect into CommonMark.

When an old (i.e., already non-current) version of a post, accessible through the post's revision history, contains Markdown that is incompatible with CommonMark, how will that version be rendered when a user accesses it? Will it still show the same HTML it once had?

And when diffs are viewed in the revision history--in the "inline" and "side-by-side" views--how will they appear? Will existing diffs (i.e., those between two successive revisions that already exist now) still render the same, no matter how old?