MOAC in OAF Custom pages

There would be property called MULTIORG ENABLE at AM. Please set that as M for multi org.

You can register custom application using API FND_MO_PRODUCT_INIT_PKG.register_application

In D2K forms below are built in APIs to change menu, form and security
    FIND_MENU_ITEM
    GET_MENU_ITEM_PROPERTY
    COPY
     DO_KEY