If I have multiple site collections and one of them is using Site Collection App Catalog, can I test the new package on it before installing on the entire tenant?

If you have the New Upgrade package on multiple site collections and you proceeded with the first upgrade (no matter using Site Collection App Catalog, or Tenant App Catalog), once upgraded on one site, the ShortPoint will be upgraded for all of them.

If the upgrade/rollback or enabling/disabling Auto Upgrade is done on one site collection, it will affect all the site collections that have New Upgrade package.

Related articles:

• I am using Site Collection App Catalog. Can I upload New Upgrade package to it?
• I cannot test the new release on the site collection that uses Site Collection App Catalog? What for can I use it then?

Main articles about New Upgrade:

• ShortPoint SPFx New Upgrade for Office 365 and SharePoint 2019
• ShortPoint SPFx Auto Upgrade Feature
• ShortPoint SPFx Sandbox Mode Feature

You may check other FAQs about ShortPoint Upgrade in this folder.