1.I 【can】tell who he is. tell在此当作 识别; 辨别意思,多与情态动词can/could/be able to连用
2.Can I tell you who he is?
3.Can you tell me who I am?
4.Can I tell you who I am?
5.Can you tell me who you are?
6.I will know who he is.
7.I will tell you who he is.
8.I can tell you who he is.
9.I couldn't remember who he 【is改为was最好,与couldn't时间一致】.
或I 【couldn't 改为 can't 与后面is 时间一致】remember who he is
10.Can you remember which way to go?
11.Can't you remember which way to go?
其它表达都正确,只是语义不尽相同.看来你真很用心啊!祝进步!