Because there are seven school years in Hogwarts.
(Unrelated to this, Voldemort made seven horcruxes.)
Use "I" when referring to yourself. Example: "I am a woman." Use "my" when referring to something you possess. Example: "My hair is long."
Use plural when referring to more than one of something. For example, "dogs" is plural for more than one dog.
The past tense of "hang" is "hung" when referring to suspending something. Example: I hung the picture on the wall. If referring to someone's death by hanging, then the past tense is "hanged." Example: The criminal was hanged for his crimes.
There are two occasions where an apostrophe would be used. Singular possessive: This is where you are referring to something belonging to one cat. The apostrophe comes before the 's'. For example, the cat's milk. Plural possessive: This is where you are referring to something belonging to more than one cat. The apostrophe comes after the 's'. For example, the cats' milk.
It is somebody or something that is the very best example of something.
You use "his" when referring to something belonging to a male, "her" for something belonging to a female, and "their" when referring to something belonging to more than one person of any gender. For example: "His car is blue," "Her house is on the corner," "Their dog is very friendly."
Orthogonal is a term referring to something containing right angles. An example sentence would be: That big rectangle is orthogonal.
"Have not received" is correct when referring to something that has not been received up to the present moment. "Had not received" is correct when referring to something that was not received at a specific point in the past.
Wrenched means to twist and sprain something, for example you would probably hear someone use the word, when referring to an injury to the knee.
Well, acquaintance means to get to know or understand something, for example; "She had little acquaintance on the subject." I'm not sure if this is the word you are referring to. :)
That is a moot point and matter for the poet to decide. My opinion is that 'Of Something' would most likely be aspects around that Something, whereas 'On Something' would be more specifically about the Something.
You use "get" when referring to obtaining something from another location, for example "get the mail." You use "bring" when referring to taking something to another location, for example "bring the dishes to the kitchen."