Hi,V1 is top input and V2 for bottom input..As you see..If i vary R4 and stablize others,the difference between V02 and V01 will change to obtain desired gain....But problem here is to eliminate offset voltage..you know..when i ground V1 and V2 and U1 , U2 comes to saturation..It's weird.That's why I create this post
Try a different simulator.