1. If you get one million dollars, what will you do?
2. Should you get one million dollars, what would you do?
3. If you should get one million dollars, what would you do?
4. If you were to get one million dollars, what would you do?
5. If you got one million dollars, what would you do?
According to a Canadian, #3, #4 and #5 are all correct and mean the same thing. They all suggest that it is entirely unlikely. However, #1 suggests that it is entirely possibel.
According to http://dictionary.cambridge.org/define.asp?key=73138&dict=CALD , people use ‘should you get....'[#2] to mean 'if you get'[#1].
According to an Englishman, #2 is a literary equivalent of #3.
I am totally confused about these contradictory statements! Does [should you get] mean [if you get] or [if you should get]? Can any native speaker help me?

1b. If you got one million dollars, what would you do?

2a. Should you get one million dollars, what will you do?

2b. Should you get one million dollars, what would you do?

3a. If you should get one million dollars, what will you do?

3b. If you should get one million dollars, what would you do?

4a. [none] 

4b. If you were to get one million dollars, what would you do?

___

All the a's have the same meaning.

All the b's have the same meaning.

Group 2 and 3 (with should) are much less used.  These rather literary forms are used mostly in poetry and song lyrics and book titles, for example, but rarely in conversation these days. 

CJ 

CalifJim

“Group 2 and 3 (with should) are much less used.  These rather literary forms are used mostly in poetry and song lyrics and book titles, for example, but rarely in conversation these days. 

CJ 

”

sitifan

“ Groups 2 and 3?”

CJ

sitifan

“

 

4a. [none]

If you are to get one million dollars, what will you do?

Is the above sentence possible?

”

It's not natural at all.