The very first day you start doing your exercises you will begin to feel a difference. As you continue daily, your musculoskeletal alignment will improve and you will feel stronger, and more flexible.
If you don't do the menus on a daily basis, you will not see the same results as if you do.
Of course you can, but if you want to see the results you came in for, then do them all.
One visit is not enough. Your body changes and transforms when you do your menu daily, and depending on your condition, you will need to get a new menu in 2-3 weeks because you want to strengthen new muscles. My first Egoscue therapist told me that I had to sign up for 8 visits to really see a difference, and I did. Yes you can feel changes after only one menu, but if you want to really make a huge change, 8 visits is highly recommended. Remember that this is for the rest of your life. This is a long term thing, and the knowledge you gain will put you in charge of your body, not having to always depend on help.
There are hundreds of exercises and I will cater to your needs. Nothing should hurt. Everybody has to start somewhere.