1.以上答案都正确,即：
I don't know how to get to the zoo.
= I don't know how to reach the zoo.
2.
1）如果后面是名词/名词短语,则用：reach...= get to...= arrive at/in/on...
如果是小地方,用arrive at；
市级以上地方,用arrive in；
有一些特殊的规定用on的,如island/farm等,就用arrive on.
如：reach the school = get to the school = arrive at the school
2）如果后面是副词,如home/here/there等,则用：reach...= get...= arrive...
如：reach here/there/home = get here/there/home =arrive here/there/home