Are all ways of solving questions allowed in the exam?

I am a mature student from Greece sitting the A-level tests this May. I am a former physics student in the university, so most of the stuff is easy for me (fortunately). As I am going through some past papers, I wonder if there is a proper way to solve something as shown in school, or covered in the textbook and any other answers get disqualified?

For example, in this exercise
https://www.youtube.com/watch?time_continue=225&v=Q8amEL91IBc

one can simply use conservation of mechanical energy to quicky solve without going through all the trouble of analyzing forces etc.

or in this exercise : http://qualifications.pearson.com/content/dam/pdf/A%20Level/Mathematics/2017/specification-and-sample-assesment/a-level-l3-mathematics-sams.pdf#page=112

one can simply find the equation of speed by differentiation and solve this in a few lines.