Does the unmarried young man who has lost one of his testicles, or who has completely lost both testicles, fall outside the scope of the rulings, commands, and prohibitions of the Qur’an and Sunnah that pertain to men, such that there is no sin upon him for looking at women or practicing masturbation, and he is not included in the rulings for men?

Masturbation is forbidden for both men and women, and there is no difference between an emasculated person and others. As for an emasculated person looking at women, scholars have differed on this:

For men whose desire has diminished due to old age, illness, or impotence, and for an emasculated person, an old man, or an effeminate man who has no desire, their ruling regarding looking is the same as that for unmarriageable kin (mahram (definition)), based on the Almighty's saying: ﴿Or those male attendants having no sexual desire﴾ [An-Nur: 31]. The preponderant opinion is that an emasculated person is like others regarding the ruling on looking, so it is not permissible for him to look at a non-mahram woman. This is the sound madhhab (definition) of Imam Ahmad and others. It is not permissible for women to be in seclusion with emasculated men, because sexual desire does not completely disappear from men's hearts, and there is no guarantee that they will not enjoy kissing and other similar acts.