AlterBrains

If sites use different files (own server folders) - you need to install/upgrade on all sites.

If sites use same files (share same server folder):
- if sites use different tables for extensions list, schema updates and extension data - you need to install/upgrade on all sites.
- if sites use same tables - you need to install/upgrade on master site only.

So we always recommend to use same database tables for all sites.

How to upgrade? Just install the new version?

Yes, just install new version. Don't de-install extension before.

I have upgraded. It is OK. Great. Thanks.