Answer 1

Originally
<str> = "012345"

// From index 0 to the last
str = str.Substring(0); // "012345"

// From index 2 to the last
str = str.Substring(2); // "2345"

// From index 0, 3 characters
str = str.Substring(0,3); // "234"

// From index 1, 2 characters
str = str.Substring(1,2); // "34"

Answer 2

No problem bro 👌