Kitniyos on Pesach

According to Bnei Ashkenaz, which foods were originally considered Kitniyos?

What other foods were added because of either similarities to kitniyos or otherwise?

Is it permissible to add items to the amount of items prohibited on Pesach? Is there an issue then of being over Simchas Yom Tov?

For Example:

Corn - unknown in Europe in the Middle Ages
Green Beans - non-Kitniyos according to some, not able to be made into flour
Soy - unknown in Europe in the Middle Ages
Peanuts - May one eat them?
Mei Kitniyos or Kitniyos Oils - [i.e. Corn Syrup, Corn Oil] Is there an issur to use them?

Besides just saying, "it's only a week why worry about it," let's get to the definitive answer!

Shalom.

Rallis

The Sefer She'arim HaMetzuyanim BeHalacha (Sham biDibor haMatchil "viHatotzeret") also discusses the major question of whether liquid derivatives of Kitniyos products (Mei Kitniyot), such as oils or syrups, are included in the prohibition against consuming Kitniyos; the Chayei Adam, in his Nishmas Adam on Hilchos Pesach (She'eylah Lamed Gimmel), seems to forbid these items as well, citing, among others, the Terumas HaDeshen (Shaiy'lot uTeshuvot Trumas HaDeshen Siman Kuf Yud Gimmel) who writes that one may use oil from Kitniyos for lighting candles, implying that one may not, however, consume it. The Avnei Neizer (Shaiy'lot uTeshuvot Avnei Nezer Chelek Orach Chayim Siman Shin Ayin Gimmel), among others, also assumes that the liquid products of Kitniyos are included in the prohibition. The Chok Yaakov (Sham Si'if Katan Vav), however, appears to take the lenient view about this, as do Rav Dovid Tzvi Hoffmann (Shaiy'lot uTeshuvot Melamed LiHo'il Sham Siman Pei Chet), who quotes Rav Shimshon Raphael Hirsch, and the Seridei Eish (Shaiy'lot uTeshuvot Seridei Eish, Chelek Bet Siman Lamed Zayin), and others; Rav Tzvi Pesach Frank, in his Sefer Mikraei Kodesh on Pesach (Chelek Bet, Siman Samech, Ot Bet, viAyin Sham biHarirei Kodesh Ha'arot 5-7) discusses this question and notes that Rav Chaim Soloveitchik allowed the oil from a certain product to be eaten, but he implies that it may depend upon how similar the original Kitniyos product is to the five species of grain that can become Chometz. Rav Moshe Feinstein, in his aforementioned Teshuvah (Sham), writes, though, that in a place where there is no custom prohibiting a particular product, one should not be stringent and avoid it.

Moed Tov!

Rallis