Faraaidh and Sunnats of ghusal

Q: While in janabah some semen got onto my leg. I did ghusal and purified myself thoroughly. Not long after I discovered the semen dried on the hairs of my leg. I scraped it off and re-washed the part as a precaution. Was my initial ghusal valid or did the dry semen prevent the water reaching the skin on the leg?

Q:

1) Please tell me I found little mucus in nose after some time of ghusal, it is valid or not?

2) I was not aware few years ago about wet dream and I never performed ghusal for that, now I know about wet dreams so one ghusal is enough for many years as I don't know how many times I had wet dreams?

3) If l forget to wash some parts during ghusal and I remember this after some hours, can I wash them or renew my ghusal?

4) Can I perform one ghusal at the same time for many purposes means janub and haiz?

Q: If a person fulfils all the fardh of ghusl that is gargling the mouth three times, making water reach the soft bone of nose three times and washing the body thoroughly such that no part remains dry, is the ghusl valid or the sunnats of ghusl have to be performed too? Does skipping the sunnats render ghusl invalid. Also one of my cousins told me that ghusl means wetting the entire body. If this is so then why does ghusl have faraaidh?

Q: Is this the correct method of ghusul? First do niyyah, then wash hands up to wrist three times, then gargle three times, then wash the private areas. Perform wudhu like normal, pour water over the head three time and recite kalima, then wipe off water from right shoulder three times then left? I have been using this method.