Hello, Navi: Sentence (1) is the only idiomatically correct sentence of the bunch. I don't find any of them ungrammatical. The others are bad to various degrees. I can't decide whether I find (2), (3), or (5) the worst. If you don't like (1), I don't recommend ruining it by changing it to one of the other four sentences. I recommend this instead:
6) He spared no words in explaining it to me.