I've researched this topic and as far as I can tell any plane can fly upside down if it's already in this position. It just needs to be angled enough so that its wings are angled upwards. I believe Boeing 777 can do this although I can't find any video proof.
But my real question is whether Boeing 777 can do aileron roll. From my understanding plane needs to pitch upwards a bit to gain altitude and then start to roll sideways. While doing this it will loose all lift and starts falling downwards until it is upside down and gains lift again. What are the requirements for this? What is the minimum speed it needs to achieve before attempting the roll? Is Boeing 777 structurally sound to survive the attempt? I imagine it was not designed for this but is it possible?
And a bonus question: can you link me a video of any bigger sized plane doing that?