Getting nudes isn't getting laid. Get her on a date instead so you both can see it all in person. People do all sorts of things with nudes and dick pics. This could very well be a man wanting to jerk off to your cock. Men do these things to men. Keep yourself safe. Sexting isn't sex. You get sex from dates. Go for dates, not sexting. The less time you spend sexting and more time going on dates, the more you're actually gonna have sex with girls.

If they are super insistent on sexting they are probably not even a woman and it's a man trying to catfish you.

Make sure you verify that she's real by either calling on the phone, getting on snapchat, or something else.

When she said her friends took her phone you should have went along with that story. When she said her friends took her phone you could have made a joke "Guess I sounded mad thirsty" and picked up the conversation to building rapport sporadically then waited till the next day to continue texting. The fact that she said she was going out with her friends and you decided to ask her to come through at the beginning showed that you were not listening. She was busy that night, should have tried to go for a date close after building comfort.

Stop being sexual. She doesn't like it. "Someone took her phone and wrote those sexual messages". Act like it was true, even if it wasn't, and assume that she's back in comfort mode. She likes your looks now she wants to see that you're a chill dude. Go back to comfort.

To answer the questions:

1. Has nothing to do with Alex. You can't just plug in these types of messages and not read what the girl is writing. You have to pay attention and calibrate. She's busy with her friends? Hmm, maybe we should plan for another day. Her friend took her phone? Hmm might be so let's just roll with it and talk normally.
2. She's not DTF it's her friend. Remember? Even if it's fake/shit test you play along with it. That's called calibration. Go back to comfort building, skip the romantic balcony shit if you dont even have one, and get to know her. Then go for the date close. If you're still matched with her and she didn't unmatch, you still have another chance.
3. NO. You should have taken several steps back!
4. You fucked up when you went sexual when she said it was her friend. You also didn't pay attention when she said she was hanging out with her friends and invited her to come through. Back it up brother, more sexual talk will only make you look like a creepo
5. Nope nope nope nope nope stop with the sexual messages just stop and bring it back to comfort.