NO. There is no 'Christian flag' mentioned in the Authorized translations of the Bible.

Yes, the Christian flag can be used to cover a casket as a symbol of the deceased's faith and Christian beliefs. It is a common practice at Christian funeral services for the flag to be draped over the casket during the service.

It could, but it would be disrespectful.

Christiandom does not have an individual, nor a specific, flag for its entirety. Some parts of it do have their own, but many do not have even that.

The Vatican has a flag, but it does not represent, or even pretend to represent, all of Christianity. If this is the flag referred to in the question, type Vatican City flag.

the flag is blue and yellow.

the christian cross is in yellow .