I have some of those adapters I bought years ago. They work, with a caveat: no way a AAA or AA will have the amp hour rating a D or C will, so while you get the voltage, battery life is a lot shorter. Good in a pinch, though.
No, but then again, for survival situations you should be replacing old D cell cell items, with aa.
Also with two aas per adapter being rechargeable and with the way that they release their energy, they can do a good job, just with less runtime.
If you have old D battery flashlights that you like, or have to continue using then you can look into converting them to led.
Regardless of D or AA, the real issue is to quit using alkaline batteries, because they leak and destroy your electronics and flashlights.
I am now "prepped" as they say with a truly camouflaged flashlight with a much longer battery life.