Divine knowledge encompasses what does and does not occur. Decree concerns the appointed existence and states of created things. Divine will means that no event falls outside Allah's will.
Will and approval must not be conflated: the occurrence of a disapproved act under divine will does not mean Allah approves of that act. Its prohibition remains.
Similarly, foreknowledge negates ignorance of a person's action; it is not, by itself, proof that the person's ability to choose has disappeared.