Assess the following business scenarios and decide which are most suitable for implementing User Advocacy Based Push Channels:
- Scenario I: A new fitness app with unique features that users are excited to share with friends.
- Scenario II: A new UPI app providing standard services similar to competitors.
- Scenario III: A gourmet food delivery service with a dedicated and satisfied customer base.
- Scenario IV: A B2B software company with a complex product requiring detailed explanations.
Select the scenario(s) where User Advocacy Based Push Channels are most appropriate.