2. Go give it your best, but act casully, don't get nervous, act as if you are the best but realise that you aren't
Preaparing for a tournament

5. Decide on an opening with which you have played many games and stick to that opening as it will allow you to even read any alterations in the game and change your offensive or defensive strategy depending on it

Step 1 is wrong. You should do some sports before the tournament but you should also prepare good for it. You cant just sit down and play chess after a 3 days break. You need to do some tactics puzzles or for through the lines in your head to be ready for the game and to avoid blunders.

#3 is about the only one I can agree with completely. Of course, that doesn't say much really. #5 when taken to an extreme can lead one to playing the London for life. Often for a major tournament, I prepare something new to keep me engaged. You always have to keep moving forward if you want to go somewhere, so I don't think opening choice should be static if you're ambitious. I don't like #4. I don't like the wording of #2, because it suggests a carefree approach. I agree that worrying about results is wasted energy, but my resolve is to fight my hardest no matter the result of the game or the tournament. I certainly care about the result, but I do my best to focus my thoughts on the present situation on the board.

7. Try this out, if you can endure remaining hungry for a while, not for too long but long enough for you to realise that you are. This could result in an increase in the functioning of the brain, which could give the edge you need. Also, if someone isn't used to playing without no food at all or running on an empty stomach, try this not
In the days I had to sit examinations (happily now very deep in the past) I used to cram right up to the moment of walking into the examination hall. And that worked for me.
But I rather think a tournament is different.
A quiet mind able to stay focussed without strain would be great. Sports people talk of being "in the zone" which I take to mean that they are cut off from outside distraction and entirely focussed on what they have drilled themselves to be able to do.
How to do that in chess? Well I don't know but from my experience of rather gruelling competitive events (bridge congresses mostly) I know that one quality needed is to be able to be uninfluenced by successes or failures as they build up in the event.
So, drawing on the experience of athletes and my own experience of lengthy competitive events I'd say one preparation is to spend some time, on the day before the event, say, throwing your mind forward and envisioning various possible developments as they could fall out - how will I feel if I lose the first game; what can I do about that; what will it feel like to win the first game easily; how should I respond to that; if I need to point out his/her flag has fallen, how will I do it, how will I feel, how to keep calm and focussed if there is a row.
And so on.
The idea is not to worry yourself but just to train some mental muscles to work without the need for much conscious thought, as athletes train their muscles by doing the same thing over and over.
And one more tip. From the Cincinnati Kid. Things have got tough in the game - it has been going on for a long time. The players take a break. The Kid stays at the table talking of this or that. But Lancey Howard leaves the playing area, goes to the bathroom and comes back pretty thoroughly smartened up with a fresh handkerchief, after shave, whatever. He proceeds to demolish the Kid.
So after each game take a while to freshen up. Take some care with appearance. Take a spare T-shirt or two. It'll help.
1. Exercise before the tournament, nothing too strenuous just your regular workout, you wouldn't want sore muscles before the game begins.