I'm trying to do this well while also doing my actual job, so updates might be a bit slow.

Setting and setting notes-  If you can't tell by now, this particular story is set in the Harry Potter universe originally made by J.K. Rowling.  As such the first and primary source shall be the Harry Potter books years 1-7.  These will trump every other content and if they disagree with something they will be the source we use.  Secondary sources will be any major official content like additional books, such as Fantastic Beasts and Tales, and online content.  I know it is not popular, but Cursed Child falls into cannon here.  The movies are... well, they're movies, and they have some massive differences from the books.  The movies will be tertiary, as will licensed content like the games.  These may expand on what is there, but any contradictions will be rated as last.  Examples might be the frequent use of wandless magic by lots of people, and the manticores from Secrets of Dumbledore.
 
Underage magic- People learn and do it.  We know that Snape came to Hogwarts knowing a lot of curses, though there's probably some exaggeration in the idea that he knew more than most graduating students.  That said it isn't something one would want to advertise, and many families, wizarding ones, don't teach their kids, even though they could do so.  I am assuming that many, but again not all, kids are pretty much allowed to do by wizarding parents as they will at home, so long as they don't get found out or make a mess.
 
Power
Wizards of Legend- These people are absolute masters of magic, and while they might not know, or even practice any given form, they can do pretty much what they want.  If there is magical bs it can easily be explained as one of their actions.
Examples include, but are not limited to
Hogwarts Founders
Merlin
Albus Dumbledore
Grindelwald
Voldemort
 
Extremely skilled wizards- We know these are powerful, and on another level from an ordinary magic user.  At times they may exceed even the above category in their field of specialty, I.E. Snape is better at potions than Dumbledore, and able to help with the ring curse.  They stand above their peers.
Examples include, but are not limited to
Mcgonagall
Flitwick
Snape
Hermione
 
Powerful wizards- This group is strong, very strong, and may exceed the above group in their chosen field, and on some occasions match even the top group.  However they lack the overall power and skill.  They're notable, and great, but aren't quite on the same level.  Most could get here with effort and lots of practice, but most don't bother.
Examples include, but are not limited to
Harry Potter- I feel the need to explain here.  Harry is good, very good, when it comes to combative magic, but he's only getting Exceeds Expectations in other fields, not Outstanding
Most of the Order of the Phoenix (First Wizarding War, by the second they're very reduced in number.)
Most Aurors
Most Death Eaters
Queenie
 
Average wizards-  They're average, maybe they're good at one or two things, but there's nothing special about these folks.
Examples include, but are not limited to
Percy
Fudge
Umbridge
 
Below average wizards- These people are bad at magic.
Examples include, but are not limited to
Merope
Lockhart
 
 
Magic of note-  Look, there are some things that just need to be talked about, and these are a few notables.

Eternal/Indestructible spells and items- These are mislabeled, they might last forever if circumstances allow, but eventually... the branch that is given to the giants is a good example, if it remains in one piece, yes, it will burn forever however if it's crushed to dust or otherwise destroyed, it won't.  The helmet from that same interaction is similar, it is indestructible, under normal circumstances; something like fiendfyre or basilisk venom could still damage it.
 
Parseltongue- Parselmouths speak it naturally and have an affinity with snakes, as well as the ability to comprehend snakes.  Other people can learn the human variant to a limited extent, but cannot understand serpents and have no affinity with them.  Dumbledore understands when the Guants speak it, but not the basilisk, Ron can mimic what Harry says, but nothing else.
 
Wandless magic- It is very, very learnable.  Almost nobody in Europe ever does though, this is a theme we will talk about.  We know that the students of Uagadou do, and primarily, use it, so it must be learnable by even children.
 
The Trace- Must be placed on children as they enter Hogwarts, and can be suppressed/broken by a driven enough student.  Tom kills several people while he should still have it, so it must be possible.  Also not particularly useful as it generates a lot of false feedback in areas where magic is constantly being used, and is often not fit for purpose except against muggle-borns and children in non-magical areas.
 
Wandlore- Muggles can and have made wands, but cannot use them except to cause a backfire on themselves. Warndlore is restricted in the same way knowing how to make weapons is in our world. You could do it if you wanted, but most don't.

Rules/Laws of magic- They're more like guidelines.  Something may be almost impossibly hard to figure out, like summoning food from nothing, or unsupported flight, but is not technically impossible.
 
Time Travel- Time travel is bullshit, the rules are as follows.
A.  Time travel is bullshit, and the only consistency is between the same type and make of device.  Not even those to study it understand it well.
2.  Time travel is extremely dangerous bullshit, and the chances of deleting yourself from history,  or really messing with the current flow of time are stupidly high.
Γ.  (Reserved for past, present, and/or future use.)
√16. Time travel is significantly safer when used for bullshit.  Using a time turner to take a nap will generally be safer than to use it to change history.
 
Fidelius Charm- This one is a mess.  The only reason I cannot see that it isn't used far more extensively in the books is that it is almost impossibly hard.  The examples we see in the story must be from Dumbledore, even Shell Cottage, and there is a lot of question about how Dumbledore didn't know who the secret keeper for the Potters was, but that must just be part of the spell, hiding who even knows the secret from those who don't.  The reason Voldemort doesn't use it is because he simply wasn't as good at charms as Dumbledore was.
Some rules that are needed for it and will be applied.
Can only be put on stationary places and pieces of land.
If too many people know the secret, the charm fails.
If nobody knows the secret, the charm fails.
Difficulty increases with size.
Outside effects, particularly harmful ones, must be blocked by the charm.