Why not? It's more flexible - will work in any country with appropriate local cable.
Perhaps the original product is better specced than the replacement you've bought.
If in doubt, isolate. Your PV inverter should not energise its output if it does not detect mains voltage, so you could get away with not isolating it if you switched the main breaker off. But it's not going to cost you anything to do it thoroughly, so don't take the chance.
Metal sheds are prone to condensation forming inside and "raining" on the contents, so you're probably best avoiding them.
Are you looking to store the BBQs or is this a place to use them in the winter as well?
Concentrated glyphosate is so cheap, I am not sure why you would bother trying to concoct something. It cost me less than a tenner for what will probably last me more than a decade.
I think a picture is in order here.
Without knowing exactly what you're asking, how about sleeve nuts and bolts through the door? No need to fix into the timber then [as such].