Citily has one subscription: Premium. It unlocks the published places in every city. There are no tiers and no bundles to choose between.
Premium runs monthly and renews automatically until you cancel. Access begins the moment you buy, and it follows the period your app store reports as paid.
Your current status is in the app under Profile → Subscription: whether access is active and how long it runs. What you bought is shown there too; the amount and the receipt are held by your store (see Invoices).
The contractual version is in the Terms of Service.