No.

You need to load the rescue os into the ram, therefore the flasher is needed but no changes will happen to the N900 by booting it. You can download the image (rescueOS-1.3.img) from this side:

https://quitesimple.org/page/N900rescueOS

Please read the documentation about rescue os how to load the image and continue reading the documentation how to reset the lock code and read more the documentation how to poweroff the device.

After reset and power off, disconnect and restart and you are done.

My live image is only for people who struggle to install the flasher and as an extra I included the rescue image.