Statement 2 :
ambigous grammer are those , for which there exists a string which is generated by the grammer has more than one parse tree.
They may be distiinct or not doesn't matter,
Because two same parse tree for any string from the same grammer, count as 2 parse tree not one.
So that's why statement 2 is not correct, because they used distinct word in the statement.
Statement 3 :
For a given grammer if there is no equivalent unambigous grammer present , then such a grammer is known as inherently ambigous CFG.
Hence, statement 2 is correct
Statement 1 : unambigous grammer , which have exactly one leftmostderivate/rightmostderivate/oneparsetree
Hence, statement 1 is correct too.
Therefore, only 1 and 3 are correct.