Coexistence of Centos on Ventoy and Reserved Partitions

[Steve2926]

If the USB drive no longer boots to Ventoy then Ventoy may not work because Ventoy checks the MBR for Ventoy boot code which has been replaced by Centos.
You need to run the Ventoy Update process so it installs the Ventoy boot code so that it boots to Ventoy.
Then from the Ventoy menu you should be able to boot to Centos on partition 3.
Also are you UEFI-booting or Legacy/BIOS booting or both?