现在完成时态,是不是用于过去一段时间内发生的动作,时间点发生的动作就用过去式?

现在完成时态,是不是用于过去一段时间内发生的动作,时间点发生的动作就用过去式?
比如:1.where have you been during the winter holiday ,Millie? look, i have bought a new computer ,---cool, where did you but it? 这两个句子都是 where 开阔头的特殊疑问句为什么前一句用了完成时,后一句用了过去式?
2. John, i have left my wallet at home, can i borrow some money from you? no problem, when did you find you had no wallet on you ?请问这一对话,前面用了完成时,后面 when用了过去式,解释一下,另: on you 能来能换with you?