S/4HANA Cloud, Private edition Upgrade Questions

[coffee_works]

Hi SAP,

We would like to seek clarification for a customer S/4HANA upgrade project that runs on SAP S/4HANA Cloud, private edition at the moment. 

Are you able to share the upgrade strategy and approach when you upgrade S/4HANA Cloud, Private edition from 1909 to latest release?

Questions:

1) Is it in-placed upgrade since Silent Data Migration (SDMI) minimizes the business downtime? Or you will system copy from BAU landscape and create a Project landscape then perform the upgrade?

2) If it is in-placed upgrade, what's your recovery strategy if the upgrade fails half-way?  

3) If it is in-placed upgrade, after upgraded DEV system running latest S/4HANA version 2023, can the SAP transport created in new DEV S/4HANA 2023 still able to transport into BAU Prod system running for example S/4HANA 1909?

Thanks.