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I said "I may be wrong" because I was not sure if it was Aristocrat. I found good pics of Fat Boy and compared to my Aristocrat and they do look different in some details.

The black handled one is...

Sterilization would be to boil in water.
I may be wrong but your adjustable (middle) looks like Aristocrat. Basically when you put a blade in it you can adjust the position of the cutting edge to...