Isn't these two programs(portion of number valudation in JS) have same output? 1 is working but 2 is not, please help me out

Question

Here are two codes:
1.
if((b.charAt(1)==8) ||(b.charAt(1)==7))
{
true;
}

else
{
document.getElementById('number1').innerHTML="**Number should start from 98 or 97"
return false;
}

2.

if((b.charAt(1)!=8) ||(b.charAt(1)!=7))
{
document.getElementById('number1').innerHTML="**Number should start from 98 or 97"
return false;
}
https://code.sololearn.com/W1QCNwuF6jlp/?ref=app