Is it sufficient for ghusl from semen to cover pre-ejaculate (madhy) and prostatic fluid (wady) that may be discharged before it? And is intention necessary to remove the impurity of these two, or is it enough for ghusl from semen to suffice for prayer in a state of purity?

If the conditions for removing impurity by washing are met—namely, its removal by the flow of water, the absence of any barrier between the water and the limb, and the water not being changed by it—then a single wash suffices for both the ritual impurity (hadath) and the physical impurity (najasa). For ritual bathing (ghusl), it is sufficient to remove any impurity present, form the intention for ghusl, and then make water reach all parts of the body. Alternatively, one can perform a complete ghusl, which begins with washing the hands and any areas affected by harm, then performing ablution (wudu'), then washing the head and the rest of the body.