Unfortunately, I don't think either of the last two you posted have been real
Edges are too fuzzy, the hand picking the wedgie on the first one is all kinds of jacked, etc etc
Ehh blur isn't the best thing to use to judge whether a booties been shooped though as focus tends to drop off pretty fast around curved edges in photos.
Though I agree that photo is a contender for being shooped. Not only is the hand janky but there does to be some clone stamp/smooth brushing on her under-bun that is visible.
Most people who for some reason photoshop butts are generally amateurs and the easiest ways to tell is honestly just to look for distorted physical space next to the stock.
Tons of times they miss this straight line in the BG which happened to get curved by the curve tool
Additionally the other best way is just to google search the image often times you will find the original source if it has been shopped.
This one could be real just because Brazil
Janky leg on this one isn't definitive proof of shoop imo. She's doing the classic ass pose which does lock in the calve muscles when she puts the left leg forward, from that angle it makes it look noodly but its the position is just doing the same thing to her calve that its meant to do to the ass, push it out.
Furthermore with the sheer amount of hard lines and straight edges in the background and foreground of this image if it was shopped who ever did it had to have spent at least 5 extra minutes correcting the space around her. Which imo would atleast show some sort of distortion or blurring somewhere in the BG when blending it back in. Unless he was really really pro.
Lastly theres some forced perspective stuff going on with the positioning of her body in relation to the foreground which could add to the illusion of the ass is fat
Otherwise I say probably real