Well,i don't know about a plastic wand,but i have a replica of a dagger as na athime but then agand the replica does have a stainless steel blade,but the handle is plastic,i don't know.
yes you can use a plastic wand the wand is just a focal point so you can use any material you want
the only way i know of to summon a demon is to use high magic to make one appear which if your still a beginner i don't think your ready for also even with protection spells you would be in danger i think you underestimate the power of a demon they are very dangerous there are few protections that can stop a demon it takes a lot of power
and yes you can put anything you like on your alter so long as it feels right to you
1. No, a plastic wand is simply that plastic. Real wands are usually some kind of wood or metal with crystals as well ( those are all organic things that can 'transmute/ transmit/carry power. Plastic does none of those things.
2. Why do you want to 'summon' a demon ? Protection or not judging by the fact your asking about a plastic wand means you must be young and therefore unable to contain/control or otherwise be 'able' to deal with something that is both strange and does unexpected things.
3. Yes thats fine the more you have of 'yourself' the better your connection to the ' otherworld' . Just make sure they are not 'too' simple ( toys/cartoon figures etc etc )
1. While i don't advise it and it probably won't do you any good, sure. You can use almost anything as a magickal instrument. But i suggest real wood. (if you need more detail about that, just ask)
2. I am sure plenty of people could give you a summoning ritual. But first i want you to clarify to me and everyone as well as yourself why you want to summon anything, what it is you want to summon, the possible reprocussions, and whether or not you think you are ready. Summoning magick has about a 70% chance of going wrong in some way, minor or major, even with defenses up. :/ Are you sure you are ready to pursue it?
3. You can put absolutely anything you use for magickal purposes, or feel spiritually connected to on your altar.
If you have anymore questions or concerns, just ask :)
I have a wooden wand. It's two years old, I carved it out of a birch tree. the thing is, that when I got the plastic one, I felt connected to it in many ways.
And about the demon ritual, I am used to summoning, and I have met demons on the astral. My first time was horrible, and I was afraid of astral projecting for a long time, and then I had to learn protection. I just need a powerful and easy ritual.