Cyclone III: Using PLL_CLKOUT (Clock Out) pin as general purpose IO?

I think, it should be clear in my post, that I used "the said dedicated clock outputs" as another word for PLLx_CLKOUT. There are no other clock outputs available with Cyclone III.

As table 7-2 is dealing with differential I/O, the said note (1) is obviously referring to the availability of differential pairs among total I/O pins. Differential clkout pairs (or PLLx_OUTPUT, which is, as you should have learned now, the same for Cyclone family) can be used as regular I/O, but not as standard differential (=LVDS data) in- or output.