@minklt
I agree with FlameTree and Alas, but go further.
(i) Ask the committee in writing and ensure the committee replies in writing.
The facts remains that your desire for a hook on a common walls notwithstanding is “minor”, you are indeed “adding” to or “modifying” the common property and so you need your work to be approved by the committee. The committee often will wave through such small works, but may also spell out their requirements. You don’t want anyone in the future arguing that you acted without approval and asking you to remove and make good the wall.
(ii) As to the shed, I’m at one with Alas. In your request by all means put all the details (colour etc). Also mention as well as anything you can find online that indicates that the shed you’re keen on has been erected in situations like yours. I did this when I asked for permission to install a storage cabinet in my car space.
(ii) (a) One more thing, you could take a photograph of how the courtyard looks from the street without a shed and indicate in your letter to the committee that the shed will not impact on how the courtyard is viewed from the street.