Many issues on example code

[Huoran559]

1、flutter pub get since low vesion % flutter pub get Resolving dependencies... The lower bound of "sdk: '>=2.3.0 <3.0.0'" must be 2.12.0' or higher to enable null safety.

The current Dart SDK (3.4.0-220.0.dev) only supports null safety.

2、FlatButton is not defined 3、The return type 'Null' isn't a 'QEntitlement' 4、Why dependency firebase? 5、Cloud you please provide a demo gif for your example?