I apologize for the confusion. It looks like BlueWallet for Android does not have an option to select the derivation path for importing a BIP39 mnemonic seed phrase. However, you can still import your seed phrase and then manually add a testnet account to your wallet. Here are the steps:
1. Open the BlueWallet app on your Android device.
2. Tap on the "+" sign at the top right corner of the screen to create a new wallet.
3. Select "Import Wallet" at the bottom of the screen.
4. Paste your 12-word seed phrase into the text box and tap "Import".
5. Follow the prompts to set up your wallet, including creating a strong password.
6. Once your wallet is set up, tap on the "Bitcoin" tab at the bottom of the screen.
7. Tap on the "+" sign at the top right corner of the screen to add a new account.
8. Select "Testnet" as the network and enter the derivation path you want to use (e.g. m/84'/1'/2').
9. Follow the prompts to set up your testnet account.
10. Once your testnet account is set up, you can receive testnet bitcoins by sharing your testnet address with others.
I hope this helps! Let me know if you have any other questions.