Is what the young man did—kissing, touching, and undressing without penetration, which led to the emission of semen—considered zina (fornication/adultery)?

The act committed is one of the reprehensible evils, and it is a type of zina (fornication/adultery). Sincere repentance (tawbah nasuh) is obligatory, with its conditions: abandoning the sin, regretting it, and resolving not to return to it. If the repentance is sincere, Allah accepts it and forgives the sin, for "the one who repents from a sin is like one who has no sin." One must strive for uprightness by: accompanying the righteous, staying away from places of vice, and diligently engaging in dhikr (remembrance of Allah) and du'a (supplication).