虚拟语气倒装,对将来的,if they were to do是were they to do,对现在的,if they

前一个正确,后一个错误.
虚拟条件句的倒装
在书面语中,虚拟条件从句有时可以不用连词if而把助动词were,had或should移至主语之前.但如从句没有were,had或should则不能这样做.如：
Should he come,tell him to ring me up.他要是来了,让他给我打个电话.
Were I in your position,I would go.如果我处于你的地位,我就去.
Had they not helped us,our experiment would have failed.没有他们的帮助,我们的试验是会失败的.

正确。

没有，对现在、将来的虚拟都可以用if they were to do或were they to do，但if they did没有did they do 这样的用法