The token that the error refers to is on line 4-expected unqualified id before '{'

Question

#include<iostream>
using namespace std;
int main ();
int i=0;{
for (int i = 0; i < 25; i++)
  {
    cout << "Hello World\n";
  }
  return 0;
}
//*************************

Answer 1

The opening bracket at the end of line 4 is causing the error.
The opening bracket shall be before line 4 and in line 3 semicolon at the end will cause an error too.,

Your code should look like this:
 

#include<iostream>
using namespace std;
int main ()
{
int i=0;
for (int i = 0; i < 25; i++)
  {
    cout << "Hello World\n";
  }
  return 0;
}
//************************* 

Answer 2

Line 3 - { required instead of ;
Line 4 - Remove {

#include <iostream>

using namespace std;

int main(){
    int i = 0;
    
    for (i = 0; i < 25; i++){
        cout << "Hello World\n";
    }
    
    return 0;
}