Nested if statements vs &&(or) operator

I've been trying to solve this https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/basic-javascript/profile-lookup/ with the following code:

function lookUpProfile(name, prop){
for (let a = 0; a < contacts.length; a++) {
  if (contacts[a].firstName == name && contacts[a].hasOwnProperty(prop)) {
    console.log(contacts[a][prop]);
  }
    else if (name != contacts[a].firstName) {
      return "No such contact";
    }
     else {
       return "No such property";
     }
}

However this page https://guide.freecodecamp.org/certifications/javascript-algorithms-and-data-structures/basic-javascript/profile-lookup proposes the following, and it works:

for (var x = 0; x < contacts.length; x++){
if (contacts[x].firstName === name) {
    if (contacts[x].hasOwnProperty(prop)) {
        return contacts[x][prop];
    } else {
        return "No such property";
    }
}
}
return "No such contact";

I also tried modifying the above to this:

for (var x = 0; x < contacts.length; x++) {
    if (contacts[x].firstName === name && contacts[x].hasOwnProperty(prop)) {
            return contacts[x][prop];
        } else {
            return "No such property";
        }
    }
}
return "No such contact";

To no avail, though. So my question is, why doesn't my code work? And why is there the need to use nested if statements instead of && operator?

Thank you for your attention.