1. Travellin farmer -: does playing a new creature on top (and therefore replacing) of travellin farmer count as causing him to leave play?
Matt stated here that you can replace the Travelin' Farmer to activate his power.
My friend (who usually plays Cornfields) doesn't like this, but then I pointed something out that made it better - Field of Nightmares (which I *hate*) cost one point and does one point of damage for every card in your opponents hand. Travelin' Farmer takes two points to play and, if you play/swap, cost you two cards. Twice the cost for the same effect.
2. The schoolhouse building - this card causes a creature to gain a flop ability from a random creature in your discard pile - does this ability stay with the creature for the game or only 1 turn and does the card that the floop ability comes from go back to discard (so could be reused again by some other means ) or do you leave the source cardof the new foolp ability with the receiving creature that gained the floop ability?
Matt stated here that the FLOOP ability only lasts one turn. Since nothing on the card requires you to do something in particular with the card from the discard pile, I'd say it immediately goes back into the discard pile (so that you could even use it again on the same turn, if needed).
3. Struzann Jinn - in a game this Jinn became floopable due to the building schoolhouse building. The Jinn card says +2 ATK for each floopable creature in play so does the jinn if flooped gain +2ATK if attacked during a turn?
According to Matt's previous ruling, Jinn would lose his FLOOP ability and regain his own at the end of your turn. Since Jinn is in a FLOOPed state, I'd say he would gain the +2 ATK.