The Central Services File and Valid Services List carry over from week to week. I was just suggesting that an easy way to test and demonstrate your integrated system is to allow your Front and Back ends to build the files by you interacting with your system. That way, you only have to make empty ones by hand.
It means how your Central Services File contents has changed from day to day, in response to the transactions.
The idea is to create some typical mixed interactions with the Front Ends and input them, possibly by hand. Some of them can be Front End inputs selected from your A1, but you need not use all of them. (In particular, "failure" Front End test cases that check that invalid input leads to no transactions are not very useful for A6—they don't lead to transactions.) Certainly you should have Transaction Summary Files that cover all of the different kinds of transactions.
No, because what we're trying to simulate is multiple Front Ends running at the same time (at various retail terminals and planners' terminals). Actually running them on different computers wouldn't add much to the assignment, so we expect that you'll run the Front End several times in a row on one computer, but they do need to be completely separate Front End runs that don't exchange information.
So, while it's fine that your Front End has its current behaviour, you still have to write a daily script to run the Front End separately and then concatenate the TSFs from each run.
You can choose. The "user" in A6 is entirely simulated.
The diagram on page 2 looks that way because I made three copies of the diagram from page 1. ("Don't repeat yourself" is good advice, maybe.) You must have different input for each of the 5 days, though it might be only slightly different from day to day.