For the best nostalgia trip, stick to the "Vanilla" decrypted IPAs.

Install the tweak. This forces the App Store to show the download button for older apps even if they aren't in your purchase history. Sideloading IPA Files via PC

The classic arcade style holds up perfectly on older screens. You won’t get the newest map expansions (like the rotating World Tour cities), but the core gameplay looks sharp.

If you are tired of re-sideloading every week, jailbreak your iOS 9.3.5 device using Phoenix (for 32-bit) or Home Depot . Once jailbroken:

The Subway Surfers IPA for iOS 9.3.5 represents the zenith of 32-bit optimization.

Hold the Power button until "Slide to power off" appears, then hold the Home button until you return to the home screen.