There are 2 options:
1, buy a dealer key from Audi then use immo data to learn key.
2, use a MQB all keys lost service, lots offering this service now!
Sync file has to come from a working key or online calculation.
3. To win the 2h work to read ecu motor or tcu, pay 100usd for sync file.
Lesson learned! ( always save sync file when doing spare key jobs)
Finally, use Lonsdor or VVDI2 to program key for Audi A2 2018. obdexpress.co.uk uploaded a YouTube video on how to use VVDI2 to program key for Audi A2 2018 when all keys lost: