Is it obligatory to make up prayers after masturbating without certainty of seminal emission, and how can one enumerate the prayers that must be made up in this case?

Ablution (ghusl) is not obligatory merely for performing the habit (masturbation); rather, it becomes obligatory upon the emission of semen. If there is doubt about its emission, ghusl is not obligatory. Nor is it obligatory to make up prayers for performing this habit.