documentation – I am Australian and I have previously traveled to Iran; Can I go to Guam without a visa?

The restriction for people who have visited Iran only applies to the "Primary" Visa Waiver Program. You are entering under a separate agreement called the Guam-CNMI Visa Waiver Program, and therefore are do not affected (and should do not request an ESTA).

TIMATIC, the database used by airlines, establishes the following with respect to the US. UU Continental (to enter under the VWP):

You can find detailed information about the ESTA restrictions at https://www.cbp.gov/travel/international-visitors/esta#

It should say "VWP restrictions", but in any case, this is not referred to when selecting Guam as the destination. Nor does the DHS page on the VWP Guam-CNI mention it at all.

Having said that, in order to reduce the amount of paperwork you must complete upon arrival, you must register here Up to 7 days before your arrival, and present a printed confirmation upon arrival.