The only way to start A Challenging Development is have already completely Looming in the Shadows the month previously.
A Challenging Development 1/6
- Spin 10 PokéStops (500 XP)
- Defeat 3 Team Go Rocket Grunts (500 XP)
- Catch 1 Shadow Pokémon (500 XP)
Rewards: 500 Stardust, 10 Pokéballs, 10 Razz Berries
A Challenging Development 2/6
- Spin a PokéStop 5 days in a row (750 XP)
- Purify 15 Shadow Pokémon (750 XP)
- Win 5 raids (750 XP)
Rewards: 1,000 Stardust, 3 Hyper Potions, 3 Revives
A Challenging Development 3/6
- Use 6 supereffective Charged Attacks in Gym battles (1,000 XP)
- Win 3 Great League Trainer battles (1,000 XP)
- Defeat 6 Team Go Rocket Grunts (1,000 XP)
Rewards: 1,500 Stardust, 15 Great Balls, 5 Pinap Berries
A Challenging Development 4/6
- Defeat Team Go Rocket Leader Arlo (1,250 XP)
- Defeat Team Go Rocket Leader Cliff (1,250 XP)
- Defeat Team Go Rocket Leader Sierra (1,250 XP)
Rewards: 2,000 Stardust, Super Rocket Radar, 3 Golden Razz Berries
A Challenging Development 5/6
- Find the Team Go Rocket Boss (2,500 Stardust)
- Battle the Team Go Rocket Boss (1,500 XP)
- Defeat the Team Go Rocket Boss (3 Silver Pinap Berries)
Rewards: 3,000 Stardust, 1 Fast TM, 1 Charged TM
A Challenging Development 6/6
All three objectives will already by complete granting you 2,000 XP for each one.
Rewards: 3 Max Revive, 20 Ultra Balls, 3 Rare Candy