AdGuard uses a server-side verification system. If a key is flagged as stolen or leaked, it will be blacklisted, and your app will revert to the free version anyway. Legitimate Ways to Get AdGuard Premium for Free
You don't need to risk your device's security with shady links. AdGuard frequently offers official ways to use their premium features for $0. 1. The Official 14-Day Trial adguard licence key free link
If the free options don't suit you, you can often find lifetime licenses for a fraction of the cost: AdGuard uses a server-side verification system