Rabbinical student
You cannot (just by looking). A rabbi generally dresses like any other observant Jew.
A Jew that does circumcision is called a Mohell
I believe the correct form of address is Reb, but you could also use the respectful term, sir.
Rabbis don't preach. However the rabbi (or any leader) of a prayer service will usually be found at the bimah, which is rarely called an almemar.Note: A Jewish prayer service does not require a rabbi.
An antonym for the word "rabbi" could be "layperson" or "congregation member," signifying someone who is not a religious leader or clergy member.
Not if used in general, as in "I spoke with the rabbi." But it is capitalized when used with a proper name, as in "Rabbi Elias was in attendance." When referring to a rabbi in writing, on first reference, capitalize before a name. On second reference use only the last name.
Originally, it was a rabbi, a rabbi, and a rabbi walk into a bar. . .
Rabbis. Here are a few examples from the Talmud. Rabbi Yochanan ben Zakkai, Rabbi Yonatan ben Uziel, Chanina ben Dosa, Bava ben Buta, Shimon ben Hillel, Rabbi Eliezer, Rabbi Yehoshua, Rabbi Yossi haKohen, Rabbi Shimon ben Netanel, Rabbi Elazar ben Arakh, Rabbi Yochanan ben Nuri, Rabbi Akiva, Rabbi Nechuniah, Rabbi Nachum Gamzu, Rabbi Yossi Glili, Rabbi Honi Me'agel, Rabbi Abba Shaul, and hundreds of others. Each of these had large groups of disciples.
Rabbi Aaron Teitelbaum and Rabbi Zalman Leib Teitelbaum
The rabbi of France
A rabbi is a teacher.
A Chief Rabbi