The story adventure has 2 endings with photos (there are more endings, around 5, but only 2 have unique photos at the end).

The 2 routes and additional 3rd run outlined in this walkthrough assume that you have the required Dakota Tokens for the special 2 photos.
You will need 70 Dakota Tokens (50 for one photo and 20 for a second one) - if you don't have them, make sure to farm them first.

The challenges, in general, don't seem to be required in order to receive a photo or enter a dialog option.
Fully confirming it in every combination would take too long, therefor whenever I have reason to believe the challenge completion is needed it will be marked (and I would suggest finishing all the challenges regardless as they give the Dakota Tokens).

Begining:
#1 - "Shannon's reward"

Dakota's house:
#2 - "Hop in"
#3 - "Dakota with a ring"
#4 - "Toilet" (50 Dakota Tokens)
#5 - "Monster dildo" (20 Dakota Tokens)
#6 - "Neighbor"

Bar:
#7 - "Drinks"

Park:
#8 - "Sunbathing"
#9 - "Sunbather's competition"

Shanon's house:
#10 - "Reading"
#11 - "Blowjob"
#12 - "Reading after blowjob"

Mansion:
#13 - "Disguise"
#14 - "Orgy"
#15 - "Shanon's meal"
#16 - "Dakota's meal"

"What's going on?" wink
"Hmm, what's in it for me? If I help you?" wink
(Challange may be needed for photo 1)
#1 photo - Shannon's reward
"Give me 10 minutes"
"I have to"
"erm"
"finish something" eggplant water wink
"Ok, fill me in on the details first."
"Have you checked out her flat?"
"Take a peek in the window."
"Sure!"
"Do it!"
(Challange may be needed for photo 2)
#2 photo - Hop in
"Maybe the kitchen?"
"The fridge"
#3 photo - Dakota with a ring
"Leave the kitchen"
"The Bathroom"
"I have a great idea!" (50 tokens)
#4 photo - Toilet
"Check the bedroom!"
"What happened?"
"WTF?"
"???"
"??????"
"What's wrong with you?"
"Of course!" (20 tokens)
#5 photo - Monster dildo
"Open the door!"
"Just open the door. You've done nothing wrong!"
"Right..."
"Open the door anyway"
#6 photo - Neighbor
"Where would she normally hang out on her own?"
"Maybe someone saw her at the bar? We should check there."
"Talk to the bartender?"
"Keep asking questions. We need more info"
(Challange may be needed for photo 7)
#7 photo - Drinks
"Huh? Why? Do they know anything else?"
"Grab yourself a drink and calm down."
"Yeah? Why not take it?"
"Sounds like you're enjoying yourself. Take it!"
"Okay, on my way."
#10 photo - Reading
"Whoa!"

"Nothing..."
"Uhhh..."
"I see!"
"I'm not sure if I can stay focused while your nipples are pointing right at me..."
"Okay, so what do we know?"
?"Check the engraving!"
"Hmm..."
"Like, longitude and latitude. Here, let me take a look..."
(Challange may be needed for photo 11)
#11 photo - Blowjob
"Very nice."
#12 photo - Reading after blowjob
"Sure, here you go!"
"What's going on?"
"Try the gate."
"Check again, there must be a keyhole or something similar."
"Weird, okay..."
"Where are you now?"
"Isn't this obvious?"
"Ofc!"
"You should change your dress!"
"100%! Do it!"
#12 photo - Disguise
"Wow, that's hot!"
"For sure!"
"Check out the bar!"
"What is going on?"
"Wow, this really really sounds like a terrible place ^^"
"How could you, if everyone is wearing masks!"
"There seems to be a story behind this!"
"You should take a drink!"
"You should take another drink!"
"You should take another drink!"
"You should take another drink!"
"You should go back to the lobby."
"Straight to the ballroom"
(Finish as you want past this point)
"What's going on?"
"Aaand?"
"Is Dakota there?"
"wtf?"
"A hammer?"
"IC! What now!"
"What?"
"WHAT?!"
"Are you sure?"
"So all good?"
"Why?"
"What's wrong?"
"That does not sound good!"
"Hopefully not!"
"Did they kill her?"
"Holy ♥♥♥♥!"
"What's going on?!"
"Why not enjoy your stay?"
#14 photo - Orgy
#15 photo - Shanon's meal
"Sure. take your time."
The End

"Why are you almost naked?"
"Yes?"
"Uhhh..."
"I see!"
"I'm not sure if I can stay focused while your nipples are pointing right at me..."
"Okay, so what do we know?"
"Check out the inscription!"
"Hmm..."
"Do you really want to know?"
"Hah, anyway, here's the address!"
"Let me guess. You found another Monster Dildo?"
"Try the gate."
"Check again, there must be a keyhole or something similar."
"Are you saying that the ring is the key?"
"So come back to your place and get him."
"And when you're here you could suck my ♥♥♥♥."
"You know, just as a small reward for my support."
"Ookay, I'm on my way..."
"Try to go through the sewer grade."
"Right"
"Try to climb over the gate."
"Try again, Shannon."
"I know how sporty and flexible you are!"
"Isn't this obvious?"
"Ofc!"
"You should change your dress!"
"100%! Do it!"
#13 photo - Disguise
"Wow, that's hot!"
"For sure!"
"Check out the bar!"
"What is going on?"
"Wow, this really really sounds like a terrible place ^^"
"How could you, if everyone is wearing masks!"
"There seems to be a story behind this!"
"I'm here!"
"The ring worked as a key."
"I'm now in the dressing room! I'll find you later!"
"You should take a drink!"
"You should take another drink!"
"You should take another drink!"
"You should take another drink!"
"You should go back to the lobby."
"Straight to the ballroom"
(Finish as you want past this point)
"What's going on?"
"Aaand?"
"Is Dakota there?"
"wtf?"
"A hammer?"
"IC! What now!"
"Yeah, I noticed as well."
"Still in the dressing room!"
"erm... "wink wink wink
":D Almost done"
"Hmm, okay"
"Yes, but some tall guys are standing in front of me. I can hardly see anything!"
"What?"
"WHAT?!"
"Are you sure?"
"So all good?"
"Why?"
"What's wrong?"
"That does not sound good!"
"Hopefully not!"
"Did they kill her?"
"Holy ♥♥♥♥!"
"So do I."
"hmmm"
"It doesn't sound like pian."
"Found you!" smile
"Why not enjoy our stay?"
"Woooooah"
"Let Dakota eat you out now!"
"While I do it to her!"
#16 photo - Dakota's meal
"Sure, take your time"
"I'll stay here and have a look at Dakota."

"What's going on?" wink
"Hmm, what's in it for me? If I help you?" wink
#1 photo - Shannon's reward
"Give me 10 minutes"
"I have to"
"erm"
"finish something" eggplant water wink
"Ok, fill me in on the details first."
"Where would she normally hang out on her own?"
"Cool, let's head to the park."
"The park? Sure!"
"I've had quite a bit of fun there!"
"You don't remember? It was with you!"
"Come on! Don't you remember that great ♥♥♥♥ in the bushes right next to the park entrance?"
"♥♥♥♥. I guess it wasn't you after all."
"Sorry, not sorry."
"Just out of curiosity..."
(Challange may be needed for photo 9)
#8 photo - Sunbathing
"Niiiiice."
#9 photo - Sunbather's competition
(Finish as you want past this point)