(a) The Mishnah prohibits using Ma'aser Sheni money to purchase Avadim, Shefachos, Karka'os and Behemah Temei'ah - because, since they are not food, they are precluded from the 'K'lal u'P'rat u'Ch'lal'.
(b) If one nevertheless did - he must eat fruit to the value of what he purchased in Yerushalayim (see Tos. Yom-Tov).
(c) The Tana does not simply declare the sale invalid (like it did in Mishnah 5) - because he is speaking either when the seller is has disappeared or be'Meizid.
(a) The Tana forbids using Ma'aser Sheni money to purchase Kinei Zavin ve'Kinei Yoldos, Chata'os and Ashamos. Kinei Zavin ve'Kinei Yoldos comprise - a pair of pigeons or young doves.
(b) The Tana forbids it - because an obligatory Korban can only be purchased with Chulin money.
(c) It goes without saying - that one cannot purchase Olos with Ma'aser Sheni money, since they are not eaten (Tiferes Yisrael).