go abroad 中没有 to ,是也是也像“go home”一样,abroad 是副词?

go abroad/ go home,两词都是adv.
为什么 adv.前原则上不加介词呢?那是因为 adv.= prep + n.就是说把一个adv.拆开,它本省就含有一个相应的介词,如果再用,就重复了：prep.+ adv.= prep.+prep.+ n.
但这个原则不是绝对的,凡事皆有例外.from 就经常放在 adv.前,一点也不错.
e.g.
1.Where are you from?where,adv.from where?正确
Where are you going to?to where 错误
2.I went abroad.
I went to abroad.to/ in/ on + abroad 错误
I returned/ came back from abroad..from abroad 正确
3.How far is your school from here?from here 正确