Major plot holes

Rating: 7/10 (27 April 2019)

I liked this movie but was super disappointed. Good for the Russo brothers to build up Infinity War and have the ending like they did in that movie with people waiting a whole year to see what happens and this is what they presented us? That's why it's really hard to make a movie about time travel. I may have missed how they explain it in the movie but I thought if you did something in the past, it affects the future? I'll explain later. They both made Hulk and Thor as laughing stocks. So here are a couple things I noticed that were plot holes.
1) WHAT HAPPEN TO LOKI?
So where was Loki in the final battle? But most importantly, where did he go when he took the Tesaract when Tony was having that "seizure"? I guess when Cap and Tony went back to 1970 to take it from that army base, than should the first avengers movie didn't happen at all?
2) CAPTAIN AMERICA PART OF HYDRA?
When Cap was in the elevator with the Hydra goons, he whispered "Hail Hydra". So now all those guys would think Captain is part of Hydra
3) THE FINAL SNAP
This one has left me very confused. I understand that the plot of the whole movie was that the avengers would have to collect all the stones and do another snap to bring back the other half of the universe back to life. They accomplished just that. But earlier in the movie did Thanos snap again to destroy the stones? That being said, Tony sacrificed himself to snap his hand that had the stones to destroy Thanos and his army? Why just him and his army?
All in all, I still thought it was a ok movie and I'll watch it hundreds of times in the future but just a little disappointed.