1) change 是瞬间发生的动作,不可能从 2012 到现在放慢脚步进行,应该改用能持续的状态:The city has kept great changes sicnce 2012.
2) met 是瞬间动作,应该改为 The two presidents have had an interview with each other for three hours.
3) leave 表示 “离开” 是瞬间动词,此处是使役动词,意思是 “使 ... 保留原来的状态”,属于延续性行为,所以 I have left the window open since early morning 是正确的。