I think bose-x answered the original question very concisely!
My CFI pointed out to me that until such time I renew my IMC rating I cannot fly in cloud in a single crew aircraft albeit I can teach IMC in VFR conditions.
You can teach basic instrument flying using your unrestricted FI rating without any further qualification however; to teach applied IF you need to hold an IRI qualification and a valid instrument qualification. You can't teach IMC, it is a state of the weather!