Each word in Group A can be paired with a unique word in Group B. What are the pairings? Why?

Group A:
apropos, doughy, gingham, mica, rebuff, scarab, squall, ukulele

Group B:
aloft, amateur, bituminous, enables, melody, phantasm, steroid, summary

Jane wants to make some toast for her breakfast. Unfortunately, her toaster is broken. Can you turn bread into toast by changing one letter at a time? Each step must create a valid word in the English language. Jane made the change in 7 steps. Can you do as well ... or better?

BREAD ---- TOAST

Private Peter Perkins wants to change his branch of military service. He is currently in the army, but wants to join the navy. To leave the army, he must get out of his tank. He then has to go on board a ship to join the navy. Change ARMY to NAVY by changing one letter at a time. The change must go through TANK and SHIP. Each change must produce a valid word in the English language. No word can be used more than once.

ARMY ---- TANK ---- SHIP...

Make SHARK (fish) evolve into TIGER (mammal) by changing one letter at a time. Each change must produce a valid word in the English language. But there is a catch. The evolution must go through VIPER (reptile) and RAVEN (bird). No word can be used more than once.

SHARK ---- VIPER ---- RAVEN ---- TIGER

Which one of the 12 members of Group B can be added to the 7 members of Group A? Why?

Group A: Arizona, Maryland, Nevada, Oklahoma, Pennsylvania, Tennessee, West Virginia
Group B: California, Delaware, Florida, Georgia, Iowa, Kentucky, Louisiana, Maine, Missouri, New Jersey, Texas, Wisconsin

Which word in Group B can be added to Group A?

Group A: castanets
existence
kowtow
venomous

Group B: gardening
lucky
mountain
restaurant