Flutter developer needed to do some fixes on existing code

I have a flutter app (connected to web and admin too) that is ready to be published, however, it's done on an old SDK version so I want to upgrade it. I've had someone upgrade the app part of it but they couldn't upgrade the web and admin. So you will have to upgrade the web and admin part of the code. I also have three things in the code that I want to fix as they're not working properly. These 3 things are: 1. mail validation on the sign up page. 2. Star rating system needs to be fixed as it doesn't count properly and 3. Views Count on a page doesn't work properly as well.