No backwards compatibility between testnet3 and testnet4 nor their respective mobile apps.

[concordium-cl]

Testnet3 and 4 as well as the matching mobile wallets are not backwards compatible, as we did change the concept of identity issuing and account creation quite essentially in testnet4. This means that you have to uninstall all previous versions of the mobile app, download and install the newest release and then create new identities and accounts for testnet4. It also means that you cannot import testnet3 wallets into the new tesnet4 wallet and your testnet3 identities, accounts and GTUs are not available on testnet4 anymore.