Grammatically, You say B'nai Mitzvah just as you would Bar Mitzvah or Bat Mitzvah.
Something that can represent adulthood and responsibility: a book, tickets to a live concert/show, a trip, money, etc.
to prepare for a bar or bat mitzvah, usually one studies with the rabbi and cantor to learn the service, Torah reading, and hafatrah reading (and also Hebrew if you don't knopw it well)-there are usually bnai mitzvah classes at the synagogue
When my twin brothers celebrated their mutual bar mitzvah, the event was generally referred to as a 'double bar mitzvah'. Of course, that was quite a while ago, way back in 5725. Maybe there's been a catchy new label invented since then, I don't know. _____ You just pluralize bar - bnai mitzvah
Old Bnai Zion Synagogue was created in 1916.
A Bat Mitzvah girl can wear appropriate formal wear, such as an elegant dress or a pant-suit.
sons
It's appropriate to dress modestly, yes.
A gift card from his favorite store or restaurant.
A good Bat mitzvah gift of money really depends on how close you are to this person. The Jewish tradition is to give gifts of money in multiples of 18.
Nahi, bnai ya tabah ki ja sakti hai nahi. It can not be created or destroyed.
Obviously, it is a difficult thing to tell someone how much money they should give as an appropriate gift for a Bar Mitzvah, since everyone's financial situation is very different and every Bar Mitzvah participant expects different levels of gratitude from different people. However, $36 is perfectly appropriate as a gift to give your classmate for his Bar Mitzvah, even though it would probably be an inappropriate amount for a close, working relative.
A friend.