It's only if United wins Europa League that only the top four clubs on the table at the end of the season will qualify to UCL.
No.
In the case Manchester United wins the Europa league this season, they will qualify for the champions league and the 5th placed team of the premier league will qualify for the champions league too.
It's even possible that 7 english teams will take part in the champions league next season. That will happen if Aston Villa wins the champions league this season without ending the premier league at top 5 positions and Manchester United wins the Europa league.
This is very funny sha, Aston villa win championship league people that loss 3:1 against PSG I am not even sure if they will qualify in this quarter finals, before I was hoping they will do something great but I have just confirmed with my eyes that PSG is very good this season and if they should meet Barcelona in the finals they will disturb Barcelona. The team you should be talking of winning the champions league is Arsenal that stand at a very big advantage over Real Madrid and I think Real Madrid is out of the tournament because the 3 goals is too much though I have I seen where a club come from behind and counter 3 goals and still win but can it happen here.