What Vault version numbers are used for pre-release Vaults on or during a pre-release?
Pre-Release Vaults are on a Limited Release Pod. They have the same version number as the last limited release which has the same set of features and functionality as the upcoming General Release.
Example, the Pre-Release version for V23R3 is V22R2.4. The following version (23R3.0 in this example) contains the same functionality plus fixes for issues identified during pre-release. At the time of General Release, Pre-Release Vaults get promoted to the latest General Release version (V23R3 in this example).
This is stated in the Pre-Release FAQ article under Pre-Release Information in the Vault Help Documentation page that is available for every general release.
Vault Help Documentation: N/A