Instead of calling it Super Saiyan 4, why not call it Super Saiyan Ozaru?

since black people are known for their black hair and gray eyes

show only the lineages of physical characteristics like for example the weasley are all red hair with freckles, or the prewett who are wizards with reddish brown hair color (traits of molly weasley nee prewett).

Lockwood

you could have added the powers of the character Jack Frost from the movie secret of the guardians because in addition to the basic powers over ice he can also fly being that the characters you are using as a base cannot

cedric is in the same year as the twins but as he has his birthday in september which is when the school year starts they had to start school the following year so he can participate in the tri-wizard tournament and the twins not because they were born in april

pure blood because you started the story talking about a descendant of merlin with morgana le fay who had his magic nucleus sealed and that the phrentice would last for several generations you can make his father being a merlin descendant and your mother being a black-prewett like that he may be heir to merlin-le fay-black-prewett. Molly was the sister of Fabio and Gideon Prewett with them being killed in the second wizard war he may be more eligible than molly weslley's offspring.

Good

Good

Demon nanatsu no taizai

Despina

Very good

Testral= invisible

make him wish chichi and buma to become saiyanjin