Unfortunately, the answer to all three questions is the same: Device Sync as a service will be switched off after September 30th. Realm SDKs as a local database will still be available as open source, but versions 20.x and later won’t be supporting a synchronisation in the cloud.
If you’ve a plan to migrate that you can share with us, and need some more time, you can open a Support case, and ask for an extension: 3 or 6 months are typical.
It should be also sufficient to ask for it through the Chat Support, that’s available in US working hours, and is included in every Atlas account. If that doesn’t suit, then any Support Contract would do (although response times may change, of course).