Okay, a few thoughts here. It sounds like your friend was using elements of traditional evocation. Older books like The Ars Goetia et al will instruct you to threaten or coerce the entity in order for it to do your bidding. Essentially you are acting as an extension of some divine authority to command obedience. I generally do not take this approach as I consider it disrespectful.
On circles: I have noticed a lot of differing opinions on circles. Many here on BALG will say they do not use them. I do use them, and this is why; whether your concept of divine essence is theocentric or psychocentric, you better bring it to the table when you evoke. The circle, for me, is an established zone of that divine essence. It is not a prison, it is not a wall. It is simply a “posted zone” where, for a time, I am the center of metaphysical existence. Think of it like this; if you have a guest in your home you are going to be respectful and offer them a nice chair. You are not going to lock them in a room or bar entry or exit. On the other hand, it is YOUR home. I consider the circle my property line and of course I keep banishing as an option for unruly guests. I also make sure I know who I am inviting in, so I will perform an evocation outside of said zone or on the astral before I go with an invocation.
That depends on a few things and really is a subjective topic. If I do not want most entities in my zone they will not be in there with me. This is not always the case, though, and it is not because of any physical circle. It is coming from me, so a physical representation is just that; a representation.
Not all of them do. I have noticed that there are not many horror stories from anyone on BALG. In my experience there most certainly are entities that are not nice or friendly. Some few really are quite malevolent and scare the crap out of you, and not in a cinematic fashion.Very, very rarely something shows up that you are not expecting, you are not going to like it, and it is not going to like you. Having that buffer is a wonderful thing in these instances, and being able to make it leave is better. When dealing with entities as well as humans the Al Capone principle is law: A smile will get you far, but a smile and a gun will get you farther.
All this being said, I have to wonder why anyone would EVOKE inside the circle. What is the point of that? Why not an INVOCATION? What is the point of differentiation between the two if the circle makes no difference? I’m not suggesting using a triangle, but I can see no added benefit in evoking INSIDE the circle.