They are meant to be one time use items but there ways to get them off. For those like in post #4 I modify an el cheapo flat blade screw into pry lever with l bend the tip 90 degrees or slightly more so I can get to the underside next to the shaft so I can slight lift up and work my way around until the clip comes off use the bushing a backing block. The length the bent areas depends on how far you got reach in to get to the shaft. Basically you releasing the spring tension as you lift up and repositioning the clip higher until you get it off. Some of clips then need the inter spring tabs flatten out some so they can be reused. The size screwdriver to use depend how much pressure you must use to release the spring tabs otherwords flimsy ones you get by with a flimsy screwdriver and heavier takes better screwdriver. You may need further mods depending what is in the way too.

I tried and have used the spring hooks to remove them but it a much harder way to remove them. Sometimes when you got replacement it is just easier to cut them off.

Here some I remove and reuse from MTD mowers. The ones below are the 5/8 version and 3/4 are a little harder to get off as they have less spring tabs width wise. As you can see you can't access the spring tabs as long as the plastic caps are on them unless you use the pry bar method or remove t he plastic caps.
[Linked Image from i.imgur.com]
I can get the 3/4 version for a couple dollars but the 5/8 ones are nearly five dollars US plus shipping so I reused them whenever I can and sometimes the OEMs will not even sell you them. They are using them on wheel spindle shafts and the brake/clutch pedals. I also have them used several other pieces of equipment over the years. There other version of the push nuts that you can not save due their design.