My friend's iPhone has a broken screen

You find Apple Authorized service providers in Vietnam by clicking here ➡️ Locations- Apple Support

Scroll all the way to the bottom, and make sure Vietnam is selected as the country in the bottom right corner of the page there. It should then let you specific a cart per region within Vietnam to look for an Authorized service provider.

1. Please do not post your IMEI here. We cannot do anything with it and it exposes you.
2. No, it will not be free. Since it's out of warranty by your own admission there is no reason for it to be free.
3. You will have to pay for a repair. The technicians at the Servicer Provider's store will tell you the cost before you need to commit to the repair.

It will depend on what exactly the repair technician finds should there be other damage other than just the screen itself. Only they can provide you with an estimate before any repairs are made.

Ngannguyen142 wrote:

...this is an Apple software bug

Not sure how a broken screen would be attributed to a software bug. Regardless, it will not be repaired for free if it is out of warranty.