Can Prod and Dev share the same AD? (SP 2016 On-Prem)

Question

We are preparing to migrate our client's SP 2016 On-Prem to SP Online.

As our first steps we are planning to:

• Create a Dev environment as a copy of the SP On-Prem (origin), but without most of the content.
• Create a Staging environment as a copy of the SP Online (destination)

To be honest I don't understand well the role of AD in these different environments.

Can Prod and Dev share the same AD? If yes, is it a good practice?

What about on our destination? How do we set Azure AD for staging?

I've sketched 2 plans:

Plan 1 - Different ADs for Dev and Prod in the origin.

Plan 2 - Share the same AD within the client's vpn.

If you can shed a light on this matter it will be greatly appreciated.

Plan 1

Plan 2

Answer 1

It is not possible to have the same Active Directory user replicated to multiple Azure AD tenants. Because of this, Plan 1 would be more appropriate if you're in a hybrid state, though you will have to maintain separate Active Directory forests.

Answer 2

Yes, you can have multiple SharePoint farms in the same domain. There is no good or bad practice about it, as there isn't anything domain specific for a SharePoint farm other than the accounts. It doesn't register any objects in AD. A good practice would be using separate SQL servers and domain accounts for each farm.