Optimal Dividend policy and optimal capital structure

You can’t ‘devise’ an optimal dividend policy – there is no such thing and you could not be asked to in the exam. What you can be asked is to discuss the factors involved in deciding on a dividend policy (such as the signalling effect, the clientele effect, etc.) and the theories relating to it (such as the dividend irrelevancy theory).
All of this is covered in the Paper F9 lectures and notes as well as those for P4.

With regard to an optimal capital structure, again you cannot ‘devise’ an optimal structure, and you cannot therefore be asked to in the exam. What you can be asked is to discuss the theories involved (in particular M&M, and also (but less importantly) the pecking order theory) and the limitations and assumptions involved.
Again, all of this is covered in our lectures and notes.