1) That's fine; I forget his name all the time, too. It's Anshoku, in case it'll drive you nuts until you find out. But yes, in all essence, it's the Juubi's chakra from the moon which causes pain to one's mind. It also turns summonings against their masters and "phases" through objects, which you get to later. Additionally, at Black Knight rank it allows the user to forget about injuries they have, as if the pain doesn't even exist (you'll learn more if you reach said rank).
2) I was looking for "portal", which you gave me. As it's somewhat difficult to word that question correctly, I would also have accepted "We use it to harm the mind" as well, which you also gave me (the summoning's part is also alright, I suppose). Now, "It can transverse through physical objects depending on the rank of the Nekura." is more of a "What it does" answer, and so is your comment about the Summoning Animals to a degree, so it should have fallen under question 1. The Bijuu and foreign chakra parts of your answer here should have fallen under question 4. I was mostly looking for how we got our Keigoku (do we mold Physical and Spiritual energy? Do we add or substitute energies to create something new? Or do we create portals to draw it from somewhere else, which is the correct answer).
3) The Mark of the Demon acts like a seal which connects our chakra to the Juubi's chakra (Keigoku) on the moon. Think of a Jinchuriki seal: it holds the Bijuu within the Jinchuriki, and allows the Jinchuriki to draw on their chakra to empower them. The Mark of the Demon allows us to create portals, as you said, and draw the chakra through the portals, as you also said. So basically correct, I just wanted to add the Jink comparison.
4) Never word it like that again. I made an announcement in the group, but I'll say it here as well: Do not say the Nekura are immune to Genjutsu. This ability goes much deeper than this, and I'd prefer if the only time the phrase "We're immune to gen" is used is as an example. (ie. "Our bodies reject foreign chakra. Because of this, we are immune to things like Gentle Fist or Genjutsu.") I can see that you tried to expand upon this, but because of the first words you used in your explanation I decided to bring this up. Yes, Bijuu refuse to harm us, and The Drain is technically passive (after an attack), but once again i don't expect you to know about The Drain at this point. Portals was also another good example, though one thing you didn't bring up that I was hoping you would is our cloaks. All Nekura have a cloak that allows us to block freeform Taijutsu, Kenjutsu, and other Bukijutsu (weapon techniques; basically all freeform). It isn't really an "ability", but it's a defense that we have at our disposal without the cost of a move or chakra.
5) Yeah, I read your question before you edited it out. <.< Our power is magnified based upon your rank. A seer's techniques do the damage as labeled, and ranks higher do more damage depending on their rank. The side-effects are also increased by the same amount, and what it can pass through is increased as well, based upon a separate system, though. *Straight from the CC Submission* "All clan jutsu submitted for checking will have the amount of damage that seers cause only written in them. For other ranks, it is as mentioned below." If you have further questions about this, feel free to ask in the group.
Alright, so now's your chance to ask about anything I've said, any other questions that you've come up with, and then I want you to perform all the techniques you've learned thus far. This way, I'll be able to see how you think the technique works, how you would use it in battle, and I'll be able to see what techniques you still have to learn.