Starting around the time your iMac was made, Apple made changes in drive model or function where the computer must be ON for the paperclip option to work. I know that affects G4 eMacs of similar vintage—we still have two—and they have the same drive type as your iMac.
If the computer will not power up, the paperclip option is likely unavailable. Time-wise, yours in "on the cusp," so that is worth trying regardless.
If the iMac can boot, there is another option, and I just conformed the system files that enable it remain in place up through at least Mojave 10.14. Create an EJECT icon in the menubar. This third-party article shows how. I've used it with numerous Macs going back to a Performa 475.
https://www.alphr.com/add-remove-eject-icon-menu-bar/
If none of the options offered work, then the chances of this being due to a disk jammed in the drive go up. Take-apart of G4 iMacs was not something Apple intended. The real danger with this is that improper reassembly of the heat dissipation system after service can fry the computer within minutes of the next startup.
Look for take apart instructions, ignoring that FAIL to mention replacing the thermal paste and using a torque driver to properly set the screws in place.
