DEXRON III or ATF4+ is good.
one is for gm and mercon is ford now days they make a dexron mercon mix acceptable to both Dexron III and Mercon V have different specs. You should not use Dexron III in place of Mercon V.
dexron 3 replaces dexron 2, so you could mix them but the dexron 3 is better
No, there is not. General Motors skipped Dexron V to bring out Dexron VI, with the Roman numeral for 6 matching the 6-speed automatic transmission introduced in the 2006 Corvette. The Clevite Kid
Yes dextron 6 can be used in applications otherwise requiring dextron 3
yes
Dexron III. You can Dexron, Dexron II, Dexron IIE, Dexron III, and Dexron V as suitable substitutes depending on availability. Lower numbers indicate a shorter lifespan of the fluid before you need to change it. Do no use Dexron IV (aka Manual Transmission Fluid) as this is likely to cause problems.
No.
Dexron V or VI
Yes . . . All dextron iii applications can use mercon v
Yes . . . All dextron iii applications can use mercon v
No you need to use Dexron VI