[Q] Help with finding and downgrading to android 2.3.5

Hi!

I am new to this site and it's the first time for me trying to downgrade my phone back to Android 2.3.5 which my phone came with. I can't find a ROM suitable for my phone (Galaxy Note N7000). I live in Sweden and the only one I could find was with the operator "Tre".
Is it okay for me to use this ROM although I'm not with that company or can You guys with greater knowledge help me find one? Is there another way to downgrade perhaps?

Thanks in advance!