Is a girl under fifteen years old required to perform ghusl if she saw a dark spot on her clothes after prayer, some of which turned white and some light yellow after drying, and she did not feel lassitude or pleasure, knowing that she felt a slight desire before prayer that subsided, and semen was not discharged with desire or contraction? And is it a condition for ghusl to be obligatory due to semen that all conditions be met, such as its discharge with desire and subsequent lassitude?

If something exits during prayer and you are certain of its exit, it is obligatory to interrupt the prayer, perform ablution, and repeat the prayer, because what exits invalidates ablution. If you are certain that it is semen (maniyy), ritual bathing (ghusl) becomes obligatory. If it is pre-seminal fluid (madhy), it is obligatory to purify the area and whatever it has affected on the body and clothes, and to perform ablution. As for vaginal discharge, its purity is preponderant, and nothing but ablution is required. If you are uncertain about the type of fluid that exited, you have the choice to assign it a single ruling from among what you are doubtful about. Some characteristics of semen might be absent, yet it still necessitates ghusl if it possesses some of its distinct properties. Not everything that exits with desire is semen; rather, what matters is the presence of the characteristics of semen.