Sorry for late reply. I was under impression that I subscribed to forums and I will get an email notification about any new question. I will have to check it out again.
Here is your answer:
Usaka - singular masculine ( usaka kamara-- his room)
Usake - Plural masculine ( usake kapare - his clothes) , usake can be used as respectful masculine in singular case also.
Iskaa - masculine, same as usaka but used when the person is present there. ( Is ladke kaa naam kya hai? -- What is the name of this boy?)
Iskee - feminine (use is same as iskaa) (iskee choodi - This girl's bangle, girl/woman is implied there by the use of iskee)
Hope this helps,