Does sleep in the mosque during Jumu'ah (Friday prayer) or while awaiting prayer invalidate Wudu' (ablution), and is it permissible to wet one's undergarments with Mathy (pre-seminal fluid) before Wudu' as a precautionary measure?

Ablution is nullified by prolonged sleep while standing, and by any sleep while lying down. As for mere doubt about the emission of prostatic fluid (madhy), it should be disregarded unless certainty is achieved. Upon certainty, it is obligatory to wash whatever came into contact with the body and clothing, and to perform ablution. It is commendable to sprinkle water on the undergarments after purification (istinja') to ward off obsessive thoughts.