Factors that break wudhu

Q: I had a cut on my knee and it bleeds, then I put a plaster on it. When I make wudhu then do I need to make a new wudhu for all namaaz?

Q: I was performing salaah and during my last sajdah I felt accumulated wind about to come out i.e. I had the urge to break wind, when I sat back from sajdah that feeling was gone. Now I don't know whether the accumulated wind came out without me noticing it, or that the accumulated wind just disappeared into my body. In such case is my wudhu nullified? Can the feeling of accumulated wind just disappear (without coming out) back into the body? Or must I regard it as having come out even if I did not feel something coming out? Should I repeat the prayer and the prayer I have prayed after it?

Q: If I make wudhu and whilst I am making wudhu I break wind, do I have to start with the wudhu again, though I never had wudhu because I never completed the wudhu?