How to solve this problem ? pls help

1 
#include <bits/stdc++.h>
using namespace std;

class A{
    public:
    int i;
    A(){
    i=10;
    }
    
    
    void display(){
        i=12;
    }
    
    
    void display1(){
        i=13;
    }
    
};

int main() {

	
	stack<A>s;
	
	A a;
	
	A *b;
	cout<<a.i<<endl;
	b = &a;
    	b->display();
        cout<<a.i<<endl;
	s.push(*b);
	
	
	b = &(s.top());
	s.pop();
	b->display1();
	cout<<a.i<<endl;
	
	return 0;
}

output : 
10
12
12

expected output :
10
12
13

b is the pointer of type A and it references object a . Now we can say b is object a , whatever changes we make to b gets reflected to a. so b works like a temporary variable if there are more than one objects. when I call display() through b then variable i of object a changes from 10 to 12 and now a.i is 12 . when next time I pop from stack does the address of object a is pointed by b or the stack address ?
How can I fix the address to be of object a always , so that when I call display1() values of object a changes to 13 ?

2

suppose there is a Class A
Now when I do stack< * A> s it gives error but when i do stack< A * > s it works fine , How?
stack< A * > s - is this means stack container contains the addresses of class A?
and why this syntax stack< * A > s is wrong ?
can anyone explain pls.

3 
#include <bits/stdc++.h>
using namespace std;

class A{
    public:
    int i;
    A(){
    i=10;
    }
    
    
    void display(){
        i=12;
    }
    
    
    void display1(){
        i=13;
    }
    
};

int main() {

	
	stack<A *>s; 
// like int * is a type hence A * is also a type
// that's why it is written like this
// actually this is a template class which takes input datatype while creation

	
	A a;
	
	A *b; 
	cout<<a.i<<endl;
	b = &a;
    	b->display();
        cout<<a.i<<endl;
	s.push(b);
	
	
	b = s.top();
	s.pop();
	b->display1();
	cout<<a.i<<endl;
	
	return 0;
}

//and i think pushing object into this stack is making a copy that's why change is not reflect. 
// so anyways now, this is a stack of pointers