Answer:
a) 炎 -> 畑 -> 累 -> 級
炎 EN, honou - flame
畑 hatake - cultivated field
累 RUI - involvement, trouble, accumulation
級 KYUU - rank, class
b) 動 -> 加 -> 吐 -> 堤
動 DOU , ugo(ku) - move
加 KA, kuwa(eru), kuwa(waru) - add, append, join, take part
吐 TOU, ha(ku) - spew, vomit, give vent to
堤 TEI, tsutsumi - bank, embankment, dike