Restriction when enabling/disabling rewards via API request

Recreate the rewards via the API, after they have been created via the API you can then manage/edit them in the dashboard as “ownership” is reatined by the ClientID that created it

No.

You might want to raise a uservoice to describe what you want to do

https://twitch.uservoice.com/forums/310213-developers

or upvote an existing one