Miscellaneous Newbie questions

No sense in putting each one in a different post.

1. What is the difference between String and string (upper- and lower-
case)?
2. Which is preferable, IntVariable.ToString() or
Convert.ToString(IntVariable)?
3. Since String is a class, why is there no String.ToClass, but there
is a StrVariable.ToString?
4. If int is a primitive, why am I allowed to say int i = new int()?

Others to come ...

String is a group of letters enclosed with two invented commas whilst string is a variable declared in c++.mind u c++ is case sensitive.
2.convert.ToString(intvariable)
3.this is bcos strvariable is a key word in c++.
4.this is bcos the new int() is a function u declared and then assigned to the variable i