The summary.
CHECK WHETHER PLAY SERVICES IS PRESENT
Some devices and regions ship without it, and applications depending on it fail entirely.
Request the lowest location accuracy that works — high accuracy consumes substantially more battery.
VERIFY SIGN-IN TOKENS ON YOUR SERVER
Anything the client sends can be fabricated, including identifiers. And keep signing in separate from requesting data scopes.
ESTABLISH WHICH BILLING RULES APPLY BEFORE BUILDING
It determines whether you may use your own payment provider. Verify every purchase server-side, and acknowledge it — unacknowledged purchases are refunded automatically.
SCOPE COROUTINES TO THE LIFECYCLE THAT STARTED THEM
Work continuing after a screen is gone wastes battery and can crash.
KEEP PLAY CONSOLE DECLARATIONS ACCURATE AS THE APPLICATION CHANGES
Inconsistency with actual behaviour is a common cause of enforcement, and verification failures make published applications unavailable.
ON-DEVICE MACHINE LEARNING COSTS NO DATA AND WORKS OFFLINE
Which matters here. Measure accuracy after conversion and inference time on a modest device.
