Is ghusl required for every prayer, with specific clothing set aside for it, upon certainty of purity, and is it permissible to perform prayer a little before its prescribed time?

It is advised to abandon performing ghusl (definition) for every prayer because it is an blameworthy excessiveness, and its cause might be obsessive whispers (waswas). Wudu is sufficient for prayer. This ghusl does not suffice for wudu, nor does it remove ritual impurity unless you intend to remove ritual impurity and wash the parts of wudu in order. One must strive against one's self in repelling obsessive whispers. Delaying prayer to perform it at the end of its time is permissible, but with attention to the obligation of congregational prayer for adult men unless there is an excuse.