Although I have not been to Anchorage in 7 years now since 2007, laws could change a lot in that timespan....
I have never boondocked in town there in my camper other than parking in my friends driveway on Government Hill in the late 1990's (just north of the A Street bridge at Ship Creek), however the times in my heydays there I have seen RV's parked at the Walmart at 88th and Old Seward behind the Dimond Center, the old Kmart building next to the Northway Mall (now Home Depot between Northway Mall and Sams Club) on Penland Pkwy.
I don't believe they allowed overnight parking at the midtown Walmart (A Street and Benson Blvd.) for quite sometime, as the last known permitted overnight parking to my knowledge within Anchorage was the Fred Meyer parking lot at the Northern Lights Blvd. and Seward Hwy. location.
I too have never seen overnight parking for RV's at the Fred Meyer Muldoon location, as I used to visit friends in the past that lived behind the East 40 bowling lanes in that same neighborhood.