1."anything"任何东西；是不定代词,常用于问句和否定句中用来代替 something,肯定句用 something,但在表示请求和建议的问句中还是用something.
Do you have anything to say?
I don't have anything to do this afternoon.
2."any thing" 任何一件事,主要用于条件状语从句中,If you have any thing,let me know.
3."many thing"这是个错误表达法,应该是many things许多事.
4."many things,许多事
I have many things to do today.
There are many things in my bag.