If you are trying it out of boredom and asking questions such questions such as the ones you stated above , I deem you too several years too inexperienced to start summoning .
You should always have a purpose when you summon things . You do not summon them just to " play" with them or just try it out for fun . If you are having to ask what needs to be done , what can happened , will it work etc , it is evident you have done no research and such a thing shouldn't be attempted .
i invoke and evoke demons.. why? to achieve higher degree of consciousness.. it worked, nothing really happens bad if you have been prepared about your rituals..
if you are bored, play games, interact with your family and friends.. don't take magick as a past time.. we took it very seriously so be serious also about such stuffs..
you are bored? that's the wrong reason to try, you will get hurt, if you summon cuz you've got nothing better to do, whatever you summon will see how unprepared you are, or realize you did it for the wrong reason and attack you.
you can summon anything astral really, dragons, demons, spirits, gargoyles, faeries, whatever. sending them back is another issue, as they might get here, see how powerful you are, and might think to stick around. you might not be able to see them, but they'll make there presence known. it works, and as i said it can be very dangerous. if they're nice, they can help you in your spell casting, or protect you for a short time.
Yeah man you don't want to try summoning anything until you've done your research and have a good reason for doing so, even if you know what you're doing if you summon the wrong spirit "just to see what will happen" you might end up pissing it off enough to do something nasty and potentially dangerous. So leave the summoning to the adepts and the studying to yourself would be my advice