Re Lukaku goal:
The Russian defender made a deliberate attempt to play the ball and messed it up. This means that a new phase of play starts and Lukaku is onside, and the original pass is void. If the ball had simply bounced off the defender or deflected off him and it was obvious that he couldn’t do anything about the touch then it would be offside, but he made an attempt to try to control / pass it while under no pressure or obligation to do so and got it wrong. Same as Mings v Man City last season, when he tried to control a loose ball with nobody near him and fudged it, and then a City player got his skates on and nicked it.