Does the habit of masturbating by pressing the thighs together and applying strong pressure to the labia cause the loss of virginity, and what is the way for sincere repentance and steadfastness upon it?

Relationships between young men and women, whether under the guise of love, friendship, or acquaintance, are not permissible in Islamic law, regardless of whether the parents are aware or not, and regardless of whether the intention is marriage or not. It is obligatory for anyone who has fallen into the sin of watching forbidden content or masturbation to repent immediately. Repentance consists of abandoning the sin, regretting it, and resolving not to return to it. Repentance erases what came before it, and Allah accepts repentance and rejoices in it. One must beware of the whispers of Satan that lead to despair of repentance, for repentance is easy by the permission of Allah. Seek help from Allah, rely upon Him, strive to remain steadfast, and be keen to associate with righteous women and occupy your time with what is beneficial.