急～～倒装句的问题。。。会追加的

应该用前者，
we have to do sth 。。。结构的否定式为：
we don't have to do sth,不是we haven't to do ...
所以倒装句的助动词还是do.
not only do we/they have to do ...

not only do we have to feed our pets 这句是对的 not only have we to feed our pets 这句好像不对的。。。。当have解释成“已经”的时候才能直接提前如 Scarcely had i collected my clothes when it began to rain.
好像没区别的？？ 呵呵 我也不太清楚，希望能帮到你。