Cities: Skylines II

In order to have 5 City Policies available you'll need to reach Milestone 10: Small City (89,700xp).

I had 17k~ population when I reached Small City but it'll vary on your experience gained.

Once you reach Milestone 10 you have unlocked the 5 City Policies:

• Taxi Minimum Fare (Milestone 4: Grand village (8,300xp))
• Pre-Release Programs (Milestone 5: Tiny Town (13,600xp))
• Advanced Pollution Management (Milestone 6: Boom Town (21,300xp))
• High-Speed Highways (Milestone 10: Small City (89,700xp))
• City Promotion (Milestone 10: Small City (89,700xp))

To activate the City Policies click the tiny city icon (City Information) next to the Demand graph for zones in the lower left of the HUD. It'll open a new window with the tabs "Demand" and "City Policies" at the top. Click the City Policies tab and then have all 5 City Policies checked to unlock the achievement.