Is it a valid statement "This will be probably used by

Just i want toknow whether this statement is valid or not"This will be probably used by JOHN"....
And one more doubt i have is

When you call a person and the person who lift the call is not the intended person what do you say???
"Can i speak to JOHN" or "Could i speak to JOHN" or "May i speak to JOHN"......
If all of these are correct which of them is very polite.....

Can any one please tell me where to exactly use "HAD"
Give me examples like in day to day converstations

please dont give explanation like we use had for Past participle or past perfect i dont know all these things explain with real examples........

<Just i want toknow whether this statement is valid or not"This will be probably used by JOHN".... >>

will be used by John

It's a little awkward put that way these sound better.

1) "This will probably be used by John."
2) "This probably will be used by John."

There'd be a number of different things you could say when you call and want to speak to John. All three of those you list are correct. You've listed them in order of politeness. "May I speak to John." would be polite enough in most cases.

The word "had" can be used in a number of ways. For example, it's the past tense of "have".

A) "When I was a child I had a toy car."
B) "I had my wallet on me at the shop but I don't know where it is now."

"Had" also serves as the past participle of "have".

C) "I have had my breakfast."
D) "I have had many different jobs since I left hgh school."

You also use "had" to form the past perfect. You can think of past perfect as a double past structure ... sort of ... at least sometimes.

E) "I was hungry yesterday because I had not had my breakfast."
F) "I failed the exam because I had not studied."

I hope this helps.