The multiple choice part is delivered using a touch screen computer and the hazard perception part records your responses through the use of a computer mouse button.
If you pass one part and fail the other you'll fail the whole test, and you'll need to take both parts again.
The questions in each multiple choice test vary according to the category of vehicle you're hoping to obtain a licence for eg a motorcycle theory test will contain specific questions that don't appear in any other test.
For the hazard perception test there are no separate versions for different vehicles, the items are drawn from the same pool, and each vehicle category takes the same test. However the pass mark is different for different categories of tests.