Rant alert!
I have only worked as an intern for an early-stage startup and my experience has been mostly bad. I believe that points 2 and 3 must be followed irrespective of the stage of your company or the seniority level of the employee.
Regarding 2nd point, I got a call (not a msg but a direct CALL) from my mentor and the Co-founder for a file that he misplaced and needed to work on and it was fucking 1 am on the 1st of January this year. 1 hour after the start of a new year. And this thing was a norm but this particular incident tops it all.
Regarding 3rd point, I was working on a file before my exams which my mentor kind of persuaded me to finish before I took my leave. It was not really possible to complete within time but I somehow did it. For context, it was my end-semester exam worth 50% of my grades and I had 6 exams on 6 consecutive days. 2 days later when he was working on the same file, he noticed an inconsistency in the data which I should have noticed as well (not blaming the unreasonable time deadline or anything). I had my exam at 2 pm (which he knew), he called me at 1 pm and then gave me a lecture on ownership and accountability. He basically said that he would not touch the file at all and I have to do it all over again ASAP. I assumed full responsibility and told him my situation and asked him to wait for me to come back from my exam. I did not really mind it since it was my mistake but I did not appreciate the fact that he did not try to cover for me or anything given the fact that I did most of the work, 12+ hours most days (even working during my lectures) and 6 days a week, even Sundays if needed. I came back at 5, saw 3 missed calls already from him, started and completed by 9 pm, and then logged out. The same thing happened the next day but this time it was an urgent file that the development team needed. Since I was the one handling data tasks and had all the files, he asked me to log in again. He then called the 3rd day again with similar 'urgent work' but this time I stood my ground and told him that I would be logging in on the next day after my exams ended. He did agree to that and yet called me to log in an hour later after my last exam.
Not a good experience for my very first internship to say the least.