How to do two-way synchronization of ics calendars?

Question

Calendar

The service generates an .ics link that can be integrated into Outlook/Google Calendar/etc.
Events received from the link are imported readonly (i.e. they cannot be changed in the client), which is what is required in most cases.
But how to:
1. Allow these events to change?
2. When the event changes, notify the service about the change indicating the new values ​​(url to register for each event).
3. If for some reason the service does not agree with the changes - notify outlook / client about an unsuccessful attempt and return the changes to the initial ones?
If it can't be solved natively with .ics - how can it? Preferably without the need to install additional plugins in Outlook.
Something similar is provided by the Google Calendar API with the watch functionwhich was successfully implemented and works fine BUT it needs to work with Outlook (and ideally with other clients as well).