Trying to reset an eMac g4 without apple keyboard

Command + R does not work on Macs that old.

You'll need a Tiger or Leopard macOS installation disk to boot from and reinstall macOS on the hard drive. The macOS version you need is deptermined by the processor speed.

700MHz or 800Mhz: Tiger

1GHz, Leopard.

See the following discussion:

I want to erase an eMac but I no longer h… - Apple Community

While Recovery Mode (Command + R) does not exist on any version of macOS compatible with PPC, you still may need to know the equivalent key on a Windows keyboard for actions like a PRAM Reset or using shortcuts within macOS for actions like Quit (Command + Q), or Copy & Paste (Command + C, Command + V), etc. You can use the Windows meta key (one with Windows logo on it) for the Command key. The Windows Alt key is used for the Apple Option (actually Option/Alt) key.

Hi,

There was an old PowerPC version (dban-2.0.0_powerpc.iso) of a free utility called DBAN. Another computer was used to burn the ISO to a CD-R. The CD contained a small Linux system, and allowed at least G3 Macs to boot (with the C key depressed). It was then possible to select a suitable wiping method for the internal ATA hard drive. Whether this would work with a G4 eMac is unknown to me, but could possibly be worth a try. However, this would not install a new system on the hard disk. If Mac system discs cannot be found (for example, via an online auction site), an alternative may be an old (free) Ubuntu live CD for PowerPC, maybe 10.04 or earlier, if it can be located (https://wiki.ubuntu.com/PowerPCFAQ).