Whenever I have tried activating any Redstone device other than a lamp it doesn't work so I was wondering if you need to level it up to do so or if I'm just missing something which I probably am.

I don't think In 1.12 there is any other Redstone features other than a lamp however it would be great to maybe have more!

Yh, the only redstone contraption you can power with the sonic is a redstone lamp. To upgrade the sonic's level you just keep using it, every level you get increases the amount of 'sonicing' you can do before needing to recharge it 

Thanks, I just thought that you could activate iron doors as well.

Oh yes sorry my bad, you also can do iron doors/ trapdoors