I know of that heirarchy... but i can find no info on the spirits it contains and without knowing their sigils it will be difficult to summon them not to mention the fact that i have no idea what each of those spirits can offer. Knowing a spirit's sigil is essential for a successful summoning as once charged it serves as a beacon to the spirit it represents alerting it to your presence and helping it find it's way to you.
Without knowledge of those sigils attempting to contact these spirits would be next to impossible. Pherhaps you could try asking a demonologist... he/she may know of those demons and be willing to divulge the information.
You will never compile a list of all demons. You won't even come close. Finding sources on more demons will prove difficult as different cultures have demonized many beings, but they are not actual demons.
A demon is recognizable by it's energy. Most time, people think they have summoned a demon but really just summoned a run of the mill spirit who will gladly watch you tremble in fear or give it unnecessary respect because you're not experienced enough to tell the difference between your own energy reaction and the actual energy present.
A sigil is not necessary in summoning anything. Helpful to those who feel it necessary, yes. But it isn't a requirement and it can be done quite easily without one.
Furthermore, if you have the name of the demon of which you wish to summon, you can create your own sigil of it. All it is, is a visual representation of who you are calling. Energy 101 would tell you that what you are putting into it while drawing it would have the same effect as whatever person had when they originally drew it.
Frankly, to the rest of your statements, you have come into this thread acting as though you were some sort of expert. You can not be an "invoker" if you have never invoked. You cannot be a summoner if you have never summoned. It's just that simple.
You lack the experience to title yourself any of these and frankly, you can't seem to tell the different between invoke and evoke. Which you MIGHT want to learn if you are planning to actually work with demons at any point in time. One is taking the being into your person, the other is asking for it to sit next to you. Might want to learn the difference before it bites you in the behind.
Invoking can be used as a term for summoning. Evoking uses force to summon a spirit, invoking asks the spirit to come to you. Invocation is a form of prayer i.e. you invoke a God to be present and listen to your supplication. You are asking that God to come to you and grant you it's power.
Evoking is asking a spirit, deity, being, ect. to be in your presence. There is no force used, it's simply asking them.
Invoking is asking them to come into your being so that you are for the moment that being, or as some would call it, possessed by the being. Again, force is not required.
Your name and your self described study suggests that you have taken beings into yourself. That is invoking. What you probably want to do is to evoke them.
