Request on Exchange Server SE CU1 Codebase and Trial Version Behavior

Dear Microsoft Exchange Team and Community,

I have questions about Exchange Server Subscription Edition (SE):

Codebase of Exchange SE CU1 vs. Exchange 2019 CU15
The roadmap says Exchange SE RTM matches Exchange 2019 CU15 codebase, with new features starting in SE CU1.
Is SE CU1 a standalone codebase or a direct continuation of Exchange 2019 CU15 with added features?
Behavior after Exchange SE trial expiration
What happens when the SE trial expires?
Are all functions fully retained?
Are any services or features restricted or disabled?
Will the server remain usable?

Thanks for your clarification!