After much internet reading on Office 365, I realize that they consist of desktop installation of the traditional (non-cloud) Office apps. Furthermore, one can even write VBA for them in the back end.
I haven't been able to find information about whether one can start up those apps using Component Ojbect Model (COM), manipulate the apps, exchange information with them, and whether their object model is the same as for the traditional non-cloud apps. Can anyone shed light on this?
P.S. Regarding the object model, https://www.softwareone.com/en-nl/en-nl-5-common-office-365-myths says "Office 365 has not had any changes in its object model or API". Not sure if this refers to the object model of (say) Excel or Word, or whether "API" means/includes COM.