Answer:
a) 炎 -> 炉 -> 戻 -> 奇
炎 EN, honou - flame
炉 RO - furnace, hearth
戻 REI, modo(ru), modo(su) - return, give back, restore
奇 KI - strange, curious
b) 訟 -> 翁 -> 習 -> 的
訟 SHOU - accuse
翁 OU - old man
習 SHUU, nara(u) - learn
的 TEKI, mato - -ish, target