Hello helping angels.

I am a big fun of N9. I have 3 of them but unfortunatelly only one has developer mode enabled since old good times when nokia provided support.

My need is only regarding changing the volume settings via the volume-up app. But i can't install it anymore since i do not have the developer mode enabled.

I tried editing it on my computer but i cannot copy it back in the right place because of acces rights issues.

I created a backup from the N9 with the enabled dev mode, and then tried to restore that backup on the other device. I didn't get a mirrored N9, most of the stuff asking for additional downloads.

I read this topic and tried different approaches, but i was not able to enable the developer mode.
I cannot install Ancelad's repository. I get an "Instalation aborted" message everytime. I was not able to install Coderus's hack either.

On almost all of the attemts to install something i get "instalation aborted". It looks like i can install stuff taht do not write on the preotected memory zone of the device.

Can you please write a small tutorial, with chronological steps, in order to succesefully enable the dev mode? I am a noob, with no expertize in kernel and other stuff.

Many thanks in advance.