Under ADR 8.2.2.8.2, within what time window prior to the expiry date of an ADR Driver Training Certificate must the driver pass an approved refresher examination to extend validity for another 5 years?

1. On the exact day of expiry only
2. Within 3 years of initial issuance
3. Within 6 months after the certificate has expired
4. Within the 12 months preceding the expiry date of the certificate