Answer 1

the 0 and 1 is the indexes of the variables. if you have ("x={0} y ={0}", x, y) then it will write x=x y=x.
or similarly if you write ("x={1} y={1}", x, y) then it will write x=y y=y.
the indexing works to indicate variable ID to print out in string. it starts with 0 and then has int numbers as ID's

Answer 2

oh well hohoho that inner structure on why in C# it is so and no otherwise should be perhaps answered by some brighter mind

Answer 3

can you please write in code what you mean