Metal Gear Solid 5 post game content.

[epicurean]

How were people able to progress the story in the post game content without doing the repeat missions with harder stipulations? I loved the game, but just couldn't beat some that said you couldn't be spotted or things like that. I was looking at online guides too. I eventually gave up because the conditions were so frustrating. Loved the game, though, but was really disappointed I couldn't play to the "true" ending.