"flutter channel master" did something wrong and "flutter" commands do not work anymore. How can I fix this?

Question

I am trying to build an app using Android studio. When building, error as shown in the picture was occurred. Error while building the app

Error message:

Because tarantula2 requires SDK version >=2.17.0-265.0.dev <3.0.0, version solving failed. pub get failed ...

In the other PC, I used master version of flutter. So I entered "flutter channel master" to change flutter version. And then lots of error occurred as shown in the following image. Error after running "flutter channel master" vol. 1 Error after running "flutter channel master" vol.2

Once it's done, none of commands: "flutter doctor", "flutter channel", "flutter upgrade" does not work anymore. It says, "no such file", and "Failed to retrieve the Dart SDK". error messages

Furthermore, I can't build the app anymore..no ▶︎ button

Please let me know if there is a solution.