Student or Learner
1) We all friends have met up at one of our friend's place.(is this correct)
2) I bought it two years ago/before (what to use)
3) My exams are starting from/on tomorrow.(what to use)
4) All pictures are in /on her phone..(what to use)
I would use "on" for the phone too, but I agree it can be mixed.
"The pictures are in here somewhere.... if I can just remember how to access them."
"I have some funny pictures of the cat that I keep on my phone."
Both sound okay to me!
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.