I use different productions because not all clients are on IRIS 2024.1+ and it's an easy way to not expose to live deployment stuff that's still under development. I believe Default Settings are a better alternative, to avoid code duplication.

Yes we usually use both, but naming should be consistent - I like DtCreated and DtUpdated because it will sort close together, but CreatedAt and UpdatedAt will do as well

You can add a custom CSS https://docs.intersystems.com/hs20242/csp/docbook/Doc.View.cls?KEY=HECUI... and set language dropdown style to display:none;