Q&A for How to Change a Sim Card in an iPhone

Try something that wont harm the circuts, like a pencil popping it up, or take it to your nearest repair shop.

If you have an iPhone on the current iOS, go to the Settings app. Then find "Sounds and Haptics". Click on "Ringtones" and there will a list of them to choose from. You can also purchase more ringtones from Apple's ringtone store.

You will not because your contacts are saved to your iCloud account or whatever other account you have selected.

If your phone is unlocked, switching from a Japanese SIM to a UK SIM should work immediately in the UK. Make sure your phone is not carrier-locked and supports UK network bands. You might need to update APN settings for the UK carrier, which you can find on their website. Make sure roaming settings are enabled if there are connection issues, then insert the UK SIM, and it should work if everything is compatible.