请教一些英语知识（比较初级的）
⒈When I was watering the garden,it began to rain.
问：此句翻译为当我在花园里浇水,天开始下雨了.为什么在the garden 前面不用加上介词IN?
⒉⑴I have sent a grate many requests for spare parts.
⑵I can buyspare part for this car.
⑶It was the last day of this year.
问：前两句FOR加上名词修饰前面的名词,译为备份的信件和这辆车的备件.但第三句的OF也是这样的形式,我想请问此时FOR和OF是否可以替换,区别又在哪里?
⒊Town Hall clock
问：Town Hall译市政厅 Town Hall clock译为市政厅的钟,那么这里Town Hall在此处是做形容词的结构吗?能不能换成a clock of Town Hall?
我的英语是自学的,可能会犯许多低级的错误,望大家见谅.