Her father gave to her when she is three year old这个句子对吗?Her father gave a dog to her when she is three year old对吗?

两个句子都不对。（第一个：give是是给的意思时是及物动词，后面必须加宾语，或者是短语give
sb sth或give sth to sb，显然，这句话少了个give的宾语sth，所以不对。第二个：从整个句子来看是过去式，因而都应该用过去时态，所以when后面引导的时间状语从句也应该用过去时态，显然是不对的，应将she is three year old改为she was three year old。）

怕是不对，看不懂这句英语要表达什么。。。

对,但你忘了把 is 变成 过去式,Her father gave to her when she is three year old?is = was , year = years, gave to her = gave it to her.her father gave it to her when she was three years old. /her fathe...

不对，give后面必须是give sth to sb或者give sb sth 的结构，这里很明显少了一个sth，所以不对。
这里gave a dog to her 是对的，但是后面的is应该改成was，因为她三岁的时候是过去的，所以用过去时。