I'm pretty sure that you aren't meant to put boiling water into hot water bottles -they should be filled from the hot tap (and a mixture of hot and cold if your hot tap is very hot). any people scalded over the years if/when they leak, split, manage to tip it over themselves trying to screw the bung back in etc.I will admit I dug mine out when I found out how much my gas bill was going to be, found it had perished since it's about 10 years old, and bought a new one. The only question is whether I'll be able to afford to boil the kettle to fill it up!
No difference in energy consumption with an induction hob. In fact as the hob is quicker the overall consumption is probably less (as there's less time for heat to dissipate into the room). Yes you could argue that a relatively thick pan is getting heated instead of a thin walled kettle, but if you empty the kettle into the pan you're going to have to heat that metal anyway.It absolutely is, yes, assuming both run on electricity. The heating element in a kettle is in direct contact with the water so more or less all the heat goes into the water, whereas with a stove there are losses up the side of the pan and downwards. It is also much quicker, which is the main reason I've always done it!
I just fill my pans with cold water and blast them on the boost setting of the induction hob. If I'm feeling parsimonious I'll fill them well ahead of time so that the cold water can absorb some ambient heat from the kitchen