According to the National Museum of the US Air Force the SIKORSKY R-4B HOVERFLY was the world's first production helicopter and was first used in combat in May 1944. What were the roles it was used in and were their any other helicopters used in combat in World War 2?
The Hoverfly was used as a search and rescue craft in the China-Burma-India theater. This site has more information and an account by one of the first pilots.
Let me leave you with this list:
https://en.wikipedia.org/wiki/List_of_helicopters_used_in_World_War_II
And especially have a look at this one: https://en.wikipedia.org/wiki/Flettner_Fl_282
I can help you answer questions concerning helicopters, unfortunately I cannot find my sources I used 2 years ago when looking into the Flettner 282(It's a adorable looking helicopter).
What it comes down to is that helicopters were in all situations experimental at best and used where required. It really was a interesting period for aviation!