Hawk37: the DC-9 and MD-80 family use bleed air to heat the wing leading edges and the horizontal stabilizer leading edges, but the system cannot do both at the same time. Later versions of the airplane had an auto-cycling feature, but the earlier versions required a manual cycle of the tail every ten or fifteen minutes (can't remember the precise number...might have been twenty). In any case, a tail cycle is required prior to commencing the approach, as the airplane is prone to ice contaminated tailplane stall issues.
OldFella: I'm not sure about older jet transports, but the airplanes that I have flown, that are equipped with thermal wing ice protection, can heat the slats in any position. The slat, if heated, is always protected...however the inner leading edge of the main wing that is exposed by an extended slat is not. Theoretically, certification should have evaluated each configuration to make sure that the requirements for icing certification were met.
The de-ice vs. anti-ice question, by itself, almost defines the ambiguity in this issue. The terms get interchanged through various publications, manuals, etc. Boeing says the primary method of operating the wing "anti-" ice system is as a "de-"icer, etc., etc.
Notwithstanding the terminology, any system that cannot function properly until ice has accreted on the surface is a de-icer. Boots are obviously the prime example, but there are other technologies that function in a mechanical manner. On the other hand, any system that is capable of preventing the ice from forming is an anti-icer. An anti-icing design may (depending on design) work as a de-icer, but a de-icing system can never work as an anti-icer. Any ice protection system that is automatically operated by an ice detector is, necessarily, functioning in a de-ice mode, regardless of capability.