Or do I need a proper sine wave one? (they are a lot more expensive – but obviously I don't want to break my computer or telly).

Thanks

A switching power supply shouldn't have any problem rectifying even crappy sine waves. They're exceptionally tolerant to abuse; mine has suffered 415V on several occasions and 115V/400Hz supplies on a regular basis and never thrown a problem.

Not without a photon beam accelerator.

It'll be ok, so long as the voltage remains as constant as possible (which is contradiction TBH) ensure the voltage doen't exceed the charger's limit or it'll eventually toast it/reduce the life span.

you have to reverse the polarity of the neutron flow

I think once you have the flux capacitor connected to the soda stream and have made the jump to hyper space you just follow the instructions on the screen and everything else if self explanatory.

AKA – no idea.

Should be fine. I've been tuning my car with one for a long time with no ill effects.