That's entirely up to the programmer. A program could create 0 files or 50 million files (or any number in between).
Not without knowing your secret keyword to decrypt them.
Without knowing the names of the files, we can't tell you 1. what they are, or 2. how / if you can get rid of them.
You will probably need a utility program that can delete the files. However, if you know the account name and password the files were created under you can probably delete them without the extra software.
There is no 'console' in C-language, but there is a standard input, a standard output and a standard error. They are pre-opened files (file-handles) you can use in your program without knowing what they actually are.
backup
Zero or more.
C programs do not require header files. If you want a C program without header files, you can simply not create them. However, you may or may not be able to include your non-header file source files.
openoffice, download the program for free, and you can create .doc files (word files) , but first read about how to use the program on the open office website.
Most, yes. Moving operating system files or program files can cause problems.
Apple has a program called Keynote which is similar to PowerPoint on a PC. Keynote files are the presentations created with Keynote.
you cant.