Yes,Christians can convert to Judaism.
But, I can't see why a Christian would want to convert to Judaism. The Bible clearly says God has made a new covenant based on the death of Jesus as "the lamb of God who takes away the sins of the world." The old covenant - on which Judaism is based - has been superseded.
Heb 10:19 Therefore, brethren, having boldness to enter the Holiest by the blood of Jesus,
Heb 10:20 by a new and living way which He consecrated for us, through the veil, that is, His flesh,
Heb 10:21 and having a High Priest over the house of God,
Heb 12:24 ....Jesus the Mediator of the new covenant, and to the blood of sprinkling that speaks better things than that of Abel.
According to Jewish law, a Kohen can't marry a convert to Judaism.
They were a group of early Christians who were in the process of leaving Judaism.
Judaism is the religion that was a precursor to Christians. The early Christians, namely the apostles, were Jewish because Jesus was still alive and Christianity had not been developed yet. Jesus himself was Jewish.
He didn't.
For Judaism: http://judaism.answers.com/jewish-history/jerusalem-in-judaism
Nothing. Jews do not seek converts. If a person wishes to convert to Judaism, they are permitted to do so, but Judaism teaches that Judaism should not be proselytized.
No, Obama is a Christian.
Yes, according to tradition.
yes
Because Christianity is the fulfillment of Judaism.
When Jesus and his followers "branched off" of Judaism.
No, the Jonas Brothers are Evangelical Christians