First things first: your Secure Key usually ships in "lockdown" mode. To wake it up, you need to locate the small, somewhat hidden button on the bottom left (usually green).
A: Physical key works anywhere. Mobile Secure Key works as long as you have the app installed (no roaming needed). SMS may fail without international roaming. hsbc activate secure key
Here is the good news for those of you who hate carrying extra plastic in your wallet: HSBC has modernized. First things first: your Secure Key usually ships