STOS, the original STOS works only with older TOS versions, up to 1.04. But there are diverse STOS fixers which make it work with higher versions, so with 2,06 too. Use search on forum, and will find plenty of threads and links about.
Best is to upgrade machine with switchable TOS, so you can have both - 1.62 and 2.06. That's been discussed too a lot.
Famous Schrodinger's cat hypothetical experiment says that cat is dead or alive until we open box and see condition of poor animal, which deserved better logic. Cat is always in some certain state - regardless from is observer able or not to see what the state is.