"Kiddush" is not a foodstuff, it is an action. The word literally means "hallowing". Orthodox Jews perform Kiddush when Shabbat begins (Friday evening), which involves the blessing of candles, wine, bread, and God's love for the Jewish people. Following that they drink some of the blessed wine and blessed bread and this leads into a Shabbat meal that takes up much of the rest of the night.
Orthodox Jews are only allowed to eat kosher foods.
bagels and lox, and cholent - though not together! Correction: Although bagels and lox and cholent are specific items that Orthodox Jews might eat (assuming they're kosher), that would make for a rather boring and not too nutritious diet. Orthodox Jews can eat anything that is kosher.
Orthodox Jewish teenagers eat the same things all Orthodox Jews eat; kosher foods of all different kinds.
So Orthodox Jews can eat it.
Orthodox Jews, as well as other Jews, are able to do whatever they want to do. Those Jews ... Orthodox, Conservative, Reform, or any others ... who decide to observe and adhere to the formal standards and teachings of Judaism do not eat pork. In that respect, they are mirrored by Muslims and Hindus. Orthodox Jews, though, are more likely to observe and adhere to that standard than Liberal Jews (like Conservative, Reform, and Secular Jews).
No. That applies mainly to Orthodox and Conservative Jews.
Only if it's kosher.
It depends on the level of observance. Orthodox Jews eat nothing BUT kosher foods.
No.
Yes, non-Orthodox Jews can become Orthodox by becoming more observant. Non-Jews can become Orthodox Jews through Orthodox conversion.
Orthodox Jews will generally only eat in Kosher restaurants. Non-Orthodox Jews who keep kosher will generally only eat vegetarian or certain fish in restaurants. __________ For Orthodox Jews who only eat kosher, they will only eat in a restaurant that is certified kosher. Kosher restaurants will display their certification to the public. Meat restaurants will have a moshgiach (kashrut supervisor) on staff during operating hours. Dairy restaurants might also but it's not a requirement, most dairy restaurants will have spot inspections. Some Orthodox Jews will not eat in any restaurant, even if it's certified Kosher.
The laws dictating food production and consumption for Jews are called 'kashrut'.