One required reading of

[Xinfu]

Are my sentences all correct?

-For this professor's course, one required reading is Romeo and Juliet. In this play, you find 'reason of'; nowadays the usual way is 'reason for'.
-Of this professor's course, one required reading is Romeo and Juliet. In this play, you find 'reason of'; nowadays the usual way is 'reason for'.

[Rusty]

For this professor's course, one required reading is ...

[Xinfu]

Thank you, Rusty, but do you agree if we change the position of the words, OF is also admissible?

- One required reading of this professor's course is Romeo and Juliet.

[Rusty]

Yes, that is admissible when you rearrange the wording.

[Xinfu]

Thank you~

[Xinfu]

Are they all correct?:

-What I am saying applies only to/for some of you.
-For/to some of you, what I am saying applies/the same thing applies.

[Rusty]

Some may use 'for', but 'apply to' is the more common collocation.
So, 'applies only to ...' sounds better.