FormGroup valueChange filter changed values in deep object

Question

I am trying to filter only changed values over FormGroup when I subscribe other functions to it. So with example, my formGroup is like

this.myForm = new FormGroup({
    name: new FormControl(''),
    address: new FormGroup({
        street: new FormControl(''),
        postcode: new FormControl('8000'),
        country: new FormControl(''),
        state: new FormControl(''),
    })
});

I have nested form with multiple fields. Now I wish to subscribe various events, over different fields. Like street has something different, a state has a different function, the country other. So I am calling subscribe on ngInit. It gives me the issue when it loads it calls multiple times so I used debounceTime to control that and make it executes after 2 mins. But then also it executes for 1 time. and gives me empty value. so I could use skip(1) in that case. But if I call multiple functions over multiple fields of address, I need to write separate subscribe over each field that would execute multiple times again.

Q1. Could I club it to single function so my valueChanges filters only changed values?

Suppose in one go I changed the city, so data in subscribe should return only address.city. I would write single function then, depending on conditions. But every time it returns whole formValues. I am expecting to filter only changed values in the form.

this.myForm.valueChanges
    .debounceTime(2000)
    .subscribe((data) => {
        console.log(data);
    });

Q2. Does writing .takeUntil(this.unsbs) would automatically unsubscribe it like this

this.unsbs(){
     this.myForm.next();
     this.myForm.complete();
}

or I need to unsubscribe to other Subscription type variable?