When you react to a series like Marvel or Star Wars, don't let comments talk you out of skipping anything. Not all of it's perfect, but all of it just adds to the lore. There are characters that come back you won't recognize, call backs you won't understand, and some bits that are actually enjoyable. I know being a reactor is a job, but my favorite reactors are the ones that ignore the negativity and give it all a shot. You may find out you enjoy something people say to skip.

24:48 Research & Development

9:54 No, there is no previous movie showing Natasha and Clint before. We learn about their past and their current friendship just like the other characters, while living/working with (and watching) them as the movies goes by.

Nick Fury's power is super human levels of Cool. 😎

And paranoia.

55:35 Missed the incredibly important mid-credits scene, where you learn who was the big bad behind the whole plot.

And the reason Steve doesn't appear to be eating Shawarma is because they brought the cast back for re-shoots to add the post-credit scene and Chris Evens had already grown a beard for the role in his next movie (Snowpiercer) and could not shave it off so it had to be carefully hidden behind his gloved hand.

The backstory for Clint and Natasha is very deep and it plays out over pretty much the entire Infinity War run.  You never really get a full "OK, here's what happened" exposition, you just have to piece it together from random mentions across a lot of movies.  Perfectly appropriate for two black ops people  :)

Tony: "Better clench up, Legolas."
Shen: "I understood that reference!"

😂😂😂

The reason Cap knew about Flying Monkeys is because he fell into his icy 70 year sleep in 1945, 6 years after he saw The Wizard of Oz and the Wicked Witch's flying monkeys.

"I see what he's doing."
There's a little girl in one of those towers that sees what Clint is doing too.

Unwritten comic book rule: When two heroes meet for the first time, they have to fight.

What Black Widow is doing is called "reverse interrogation": the target is so desperate to obtain info from you that he fill the blank himself to confirm his own theories.

Ashley Johnson's role was slightly bigger, but a scene she was in got cut. In it, Cap is having coffee at the café outside Stark Tower, and she's his waitress. She seems a little flirtatious toward him, but Cap doesn't bite before she walks away. Stan Lee is sitting nearby and urges him to ask her for her number.

This is the quality of superhero movie which you get when the writer/director actually READ comic books as a child and who is a master of writing for an ensemble cast. The movie also mimics early Marvel comics in which two superheroes who met for the first time actually fought each other because they assumed the other was a villain.

37:52 - That’s Harry Dean Stanton right there. Famous for playing Brett, the first Nostromo victim in the movie “ALIEN”. Passed away in September 2017. Wonderful and amazing actor.

It's insane in my brain that this movie is almost 15 years old. Feels like yesterday.

Edit: Everybody says "Ooo Ashley Johnson. Critical Role!" All I remember is cute little Chrissy Seaver from Growing Pains. 😁

As for Hulk's self control, he seems to be more calm and clear headed if he is let loose intentionally or if he's been Hulk for a while enough to calm down.  If stress on Banner overwhelms him, it brings out a rage fueled, seeing red uncontrollable Hulk.

The "flying monkeys" reference goes to the movie The Wizard of Oz, the Wicked Witch of the West's flying monkeys, her personal henchmen. When Tony invited Banner to Stark Towers, saying it's all R & D, the R stands for research & the D stands for development

You missed the first of the two credit scenes - the important one. Some advice on mid and end credit scenes: they can appear anywhere - before the start of the credits, in the middle of the credits, and / or at the end of the credits. There may not only be one extra scene. One upcoming movie has 5 mid and end credit scenes. Personally, I would advise that unless you are actually going to watch all of the credits, I would google "How many mid / end credit scenes are in <insert name of the movie>?" There are several sites that will give you the answer including where they appear,  but some may also spoil what the scene is actually about, so be cautious when reading.
To answer your question about Stan's cameos, yes he is always in the movies, up through the 4th Avengers movie. Stan passed away before the completion of "Avengers 4", but had pre-filmed his cameo. Stan also did cameos for the following Marvel television shows: "Agent Carter", "Agents of S.H.I.E.L.D.", "The Gifted", and "Runaways". He appeared as a photo or artwork in the Netflix series "Daredevil", "Jessica Jones", "Luke Cage", "Iron Fist", "The Defenders" and "The Punisher", as well as the Hulu series "Cloak & Dagger".
Finally, I have to agree with the commenter that recommended "Agents of Shield". It really is a great series. But, because it does line up with the movies, there are references to events in the preceding MCU movie in at least the first listed episode following that movie. So, you should watch Season 1 in the following order to avoid spoiling movie revelations:
"Iron Man 3"
"Agents of Shield" Season 1, Episodes 1-7
"Thor: The Dark World"
"Agents of Shield" Season 1, Episodes 8-16
"Captain America: The Winter Soldier"
"Agents of Shield" Season 1, Episodes 17-22

That Avengers circle shot is so cool, whedon was very good at servicing fans with hype moments that fit the characters every time.

Yes, that's the origin of the "I understood that reference" meme.  Flying Monkeys are from Wizard of Oz, Cap is old enough to have seen that on release in theaters or read the book.