Changing ApplicationID

We can register any device for any application without specifing AppEUI (DevEUI and AppKey needed only for Lorawan<1.1, we must register proper application with service profile and specify device profile ). We can see AppEUI in raw Lorawan frame in JoinReq. I can make static external table (AppEUI and AppID key-value pairs) and register device according this table, but I want make device registration process more simplest: with DevEUI and AppKey only, registering device by my external software via API for dumb app, then get AppEUI from API (from device) and move my device to proper application.

Can I register device in dumb app (for example, appid=1), then get AppEUI from JoinReq and move device to properly application?

I try API func [PUT /api/devices/{device.dev_eui}] - Update updates the device matching the given DevEUI, but “applicationID” property for changing applicationID not worked for me for existing and joined device. Its bug of feature?

Where I can get AppEUI for joined device (not in live mode, interested some time after join procedure)?