There is one Sabbath per week Sabbath means Saturday.
Two major religions. Judaism and Christianity. (Although some Christians do not)
The sabbath is a day of rest, and there are 3: 1. Fridays for Muslims. However, Fridays for Muslims are not viewed as the God rest days after the universe creation as claimed by Jews and Christians....
challah
That depends on the religion. In the majority of Christianity, the Sabbath is celebrated on Sunday. For further reads, see link below.