1no , that's not right earendil . depends on what type of p-n junction is used. if it's Si , then the cutoff voltage is 0.7 , if it's Ge , then 0.3 , so depends as it's unspecified we take it as Si .
it behaves as short only when V > 0.7
I think we should be given the fwd bias resistance . dunno of any relation b/w rvrse bias and fwd bias .