1. I assume Iris pollen should behave like lily and one can take some fresh anthers, air dry them (film canisters work well), seal it and freeze it. Let the canister warm before opening it to prevent condensation on the pollen.

2. Experience only tells.

3. Read up if others tried it, but probably you will find little in the literature. Try it.

4. When making very wide crosses repeated pollinations over days helps and making crosses using various cultivars / genotypes can increase finding a combo that is more compatible.

Iris pollen can indeed be dried and frozen and remain viable for a couple of years. If not frozen, it is still good for a while. Iris breeders have successfully mailed pollen around and shared it. Works fine.
I expect this would also work for otehr plants in the family.
Walter