In scenario 1, I would tell my BCTAL teacher that the other intern had gotten a ride from another person and then they rode the bus back to their home campus and the other person told me not to tell anyone.
In scenario 2, I would tell them no I will not sign them in and out because they never rode the bus or showed up to site school so all of the fault will fall on their shoulders and not mine.
In scenario 3, if I saw that happen, I would let the BCTAL teacher know about it the following time I saw her and tell the person they were wrong
On scenario 4, there is harm done when you walk into your site school out of dress code. You are setting an example to the students on how teachers dress. If you were to walk in your classroom inappropriately dressed, Mrs. Petty could be there checking on you, watching you walk into school and making sure you are dressed in your appropriate attire so you could get in trouble anyway