They regularly went to the Temple and synagogue. They observed the Jewish holy days. The modern-day faith group that is closest to the primitive Jesus movement is probably Reform Judaism. Again, this is just my personal opinion. There are probably more definitions of this term than there are religions in the world.
None are completely satisfactory.
Correct beliefs about deity . If a single, indivisible God exists, then Islam, Judaism, Sikhism and a few others are contenders.