iMac not working after erasing hard drive

Internet recovery was added to the 2010 models as a firmware update somewhere back in the MacOS Lion era. Unfortunately it also quickly became slow and unreliable. You could try a hardwired ethernet connection and giving it more time, but success stories in 2021 are rare.

For the DVD recovery insert the DVD and restart holding 'C' (or option).

Note: DVD recovery may only work with the original install DVD that came with your iMac. Install disks for other macs may not work.

As a third option you can use a Mid2018 or older Mac to create a bootable USB installer. https://support.apple.com/en-us/HT201372

Sure, Tdids... I don't think your iMac does Internet Recovery Though.....so what you'd have to do is do a reset smc/pmu followed by a zap pram....here's how: for the 1st one, shut down your iMac, disconnect the power cable from your iMac, and wait about a minute or so, then plug in the power cable and press the power button, and immediately do the 2nd one, Hold down Apple+Option+P+R on the keyboard for 3-4 chimes/bongs and away you go....then just hold down the "Option " key to invoke the startup manager, and slide the dvd into the dvd slot label face up, and it should take it.....the startup manager will show all potentially bootable drives, be they from a USB stick/dvd or from wherever....pick the dvd and continue.... if you have done the 1st and second things I mentioned, then try Option+Command+R on startup and see if it'll boot up to Internet recovery....if it does you'll see a spinning globe and a progress bar on your screen.....if not, then restart and try the startup manager option....

good luck to you

John b

Insert the install disc, restart and hold the Option key.