How can a Windows CalDAV app use Apple Account authorization for iCloud Calendar?

Apple Support article 121539 describes Apple Account authorization for supported third-party apps that access iCloud Mail, Calendar, and Contacts: https://support.apple.com/121539

An Apple DTS engineer directed developers to the “Express interest in Auth 2.0 for iCloud Mail, Calendar, and Contacts” form: https://developer.apple.com/forums/thread/825772

I develop Zefir Calendar, an independent Windows desktop app built with Electron. It currently accesses remote iCloud calendars through CalDAV with the user's Apple Account email address and an app-specific password. It supports personal and shared calendars and event reading, creation, editing, and deletion according to the user's permissions. We want to request Calendar access only.

A related discussion says the interest form requires an App Store URL: https://developer.apple.com/forums/thread/847329. A Windows-only app has no Apple App Store URL.

Could an Apple engineer clarify:

1. Can an independent Windows app use this authorization flow? If so, how should a Windows-only developer submit the interest form without an Apple App Store URL? Is paid Apple Developer Program membership or separate approval required?
2. What registration, service, capability, or entitlement is required? Is there technical documentation for the flow and its Calendar scopes?
3. Can authorization be limited to Calendar, and does it support read/write access to personal and shared iCloud calendars?
4. Are the granted credentials used with the existing iCloud CalDAV service, or with a different API? What are the supported token refresh, revocation, and desktop callback mechanisms?

This question concerns authorization for remote iCloud Calendar data, not Sign in with Apple for identity or EventKit access to local device calendars. Our goal is to replace app-specific passwords while preserving our CalDAV functionality if Apple supports it.