بسم الله الرحمن الرحيم
(1) Ghusl does not become fardh if one urinates while sleeping, rather it is just enough to wash the place and cloth where the impurity is smeared. However, if someone does complete ghusl then too the impurity will be removed and it is not necessary to use soap for the removal of impurity.
(3) There is no specific method for this. There is no harm in whatsoever way you use it.
(4) The use of water is enough for the removal of impurity. The use of soap is not necessary.
(5) It is better to remove the impurity first and then make wudhu.
Allah knows Best!
Darul Uloom Deoband