adding favorites in Contacts/Phone and having lots of problems

(Device is fresh OOB iPhone 12; iPhone 12 is not listed in the device picker pulldown, so I picked generic iPhone)

I've been trying to add Favorites in Phone (or from Contacts) for an hour now and am having LOTS of problems. There are certain contacts that, when I add them, trash all the other Favorites I've already added. (Was showing, say, five Favorites. Add another. Suddenly that's the only one showing.) And then that contact has to be deleted multiple times before that contact, too, is gone from the Favorites list and I start over. The contacts that cause this problem seem to be repeatable, but I can't say what makes them different from the other contacts added without problems.

Other contacts, once Favorited, seem to preclude adding any more favorites. I select and add, but they don't appear in Favorites.

Most of these problems seem to start appearing when I add a contact that has multiple phone numbers. But I don't think these are the only Contacts I added with multiple phone numbers.

I have three sources of Contact info: iCloud, Gmail, and Outlook. I have tried with both iCloud and Gmail set as Settings|Contacts|Default.

Oh, and adding both a Contact's Mobile and Home numbers as favorites seems to be problematic as well. I see two stars in the Contact; only one entry in Phone Favorites.

Am I just missing something about how this is supposed to work? (Coming from a decade on Android but a regular iPad/Mac user as well. I setup the iPhone with a Restore from iPad; did not try to transfer from Android using the Android App/iPhone OOBE.)

Also, I have an iPhone for Dummies question about Phone|Favorites|Add: why, when I'm adding Favorites to Phone, does it offer up anything for a contact besides phone numbers? What's the meaning of, say, adding a FaceTime contact to the Phone Favorites?

Thanks in advance for any help. I hate to be getting this frustrated when I'm just scratching the surface of what I need to setup to use my brand new iPhone...