No unless they were added, 92 is 3fe engine and semi float rear axle. Diff locks started on 93s with full float rear axle and 1fzfe engine. It has a cdl button which locks the tcase
Heater valve and hoses are original any hose with a cotter pin is original. Look at the phh which is above the starter if it has cotter pin it is original. I would save a couple grand to get everything under the hood fresh.
You should if you have gone this far change those original heater hose valve and hoses. At 27 years old they are done and ready to die. Good luck with the sale
You can unplug the switch and put a jumper in the harness, if the center diff lights up now it will allow the diffs to lock, this tells ya the wiring is good , unless burnt bulb, then you would just need clean the switch or replace