Interesting Code in Cpp

I was just trying to clear some doubts on the sizes of pointers returned by the cpp compiler and I came across this anomaly or we can say a type of vulnerability in cpp, I had studied about this but had never done this practically. I was trying to access the elements of a char* and by mistake gave the end limit more than the number of letters in the string, but surprisingly I got the output which I shouldn't have got. I got the values stored in the ROM as the char* data is stored in the ROM segment of the memory.

This is the code which was implemented in online compiler of Programiz and the output which I got as a result :-

#include<iostream>

#include<limits.h>

using namespace std;

int sum(int a, int b){

    return a+b;

}

string sum(float a,int b){

    return "Foo";

}

int main() {

    const char* s="Him\0esh";

    string s1="Himesh";

    char d='d';

    cout<<"Hola Todo El Mundo!\n";

    /** Getting the size of below string as 7 **/ 

    cout<<sizeof("Himesh")<<endl;

    

    /* But the size of the below variable(string) is 

     * being given as 8 

     */

     // We can't change the char* bcz it is stored in the ROM

    //  s[6]='a';

    cout<<sizeof(s)<<endl;

    //And size of s1(string var) is being given as 32    

    cout<<sizeof(s1)<<endl;

    cout<<sizeof(float*)<<endl;

    cout<<s<<endl;

    // Accessing memory and changing it 

    for(int i=0;i<300;i++){

        s1[i]=char(((i)%26)+65);

    }

    for(int i=0;i<30;i++){

        cout<<s1[i]<<" ";

    }

    cout<<endl;

    // Accessing the ROM, not belonging to me

    for(int i=0;i<3009;i++){

        cout<<s[i]<<" ";

    }cout<<endl;

    

    /** Why the compiler is considering the below number as a double? **/

    // cout<<sizeof(11.1);

    return 12343;

}