Since you’re mine, I’ll take this.
1. As an older student, you will not participate in the Sorting. That is for the babies, let them have their day. If you’re transferring a student from another school, or even homeschooling, they’d have met with the Headmistress prior to the Opening Feast ceremony. Think of it like switching schools in real life, you’d need to get everything done before the start of school. This meeting is where you’ll be Sorted, by the hat and all.
For the dormitories, it’s probably be left until the day he came to school. Surprise and all, but that’s how it works for most students. They put their trunks on the train, and they end up in their dorm.
2. You’d be correct to think that there is a lot of inbreeding within the Pureblood world. That’s also true within the canon verse. I think, with the case of many Pureblood families, muggle disorders are not very prevalent. I believe there are some magical ailments that might touch on this issue, but it might require more research and perhaps another mod’s opinion. I do, however, think that issues being passed down through the years is valid in Pureblood families, like you said, in the case with the Blacks.
3. We have a very vast range of characters with differencing sexualities and genders. I believe, we’ve had it all, and I myself play a few of them. We are an open and accepting community, at the first and forefront. That said, our world is set in the 1940s. Transgendered was not a word at this point, sexuality was not explored, at least not in the public eye. To be gay was considered a crime, and pursing could have consequences in character. Check out this
thread to give you a better idea of what it might have been like for these characters.
4. You are correct. What you are missing is the key point, however, that Magical Levels can be earned. If you brought in a student as a first year, their levels might look like C1, D2, T1, S0. You can’t do much, but you can always make the attempt. Take Charms for example. As a rule, we say you might be able to perform a spell magic a level above your own, but can perform all the spells at your levels range. (So, all the levels at 1.) As you take classes, participate in extra activities, you gain more levels. You can even continue earning levels into adult hood. However, if you are seeking levels above and beyond the realm of normal, such anything 15+ than yes, a Special Request is required.
Anything other classes, like Potions and Herbology, are just played out. You can be as good as you want, so long as you’re not making Potions no one else can make. It’s all within reason, and we give our players space to explore that.
5. Baby, you will get a mentor once you’re profile gets approved, no worries. We don’t let new babies fall through the cracks.