Answer 1

Sequential Control Structure refers to the order in which a program executes its code.
as a general rule code is execute sequentially meaning the first line is executed first and the second line is executed second and so on.

Having said that a lot of functions, methods or statements will stop a program from running sequentially, such as
for/while loops, calling functions or anything else that can be considered apart of the iteration or selection control classes as the use of these will change the order in which the code is executed.

Hope this clears things up a bit..