解：?$(1)$?∵點(diǎn)?$P $?在?$x$?軸上
∴?$m - 1 = 0，$?解得?$m = 1$?
?$ $?則?$2m + 4 = 2×1 + 4 = 6，$?∴點(diǎn)?$P $?的坐標(biāo)為?$(6，$??$0)$?
?$ (2)$?∵點(diǎn)?$P $?的縱坐標(biāo)比橫坐標(biāo)大?$3，$?∴?$m - 1-(2m + 4)=3$?
?$ $?即?$m - 1 - 2m - 4 = 3，$?解得?$m=-8$?
?$ $?則?$2m + 4 = 2×(-8)+4=-12，$??$m - 1=-9$?
∴點(diǎn)?$P $?的坐標(biāo)為?$(-12，$??$-9)$?
?$ (3)$?∵點(diǎn)?$P $?在過(guò)點(diǎn)?$A(2，$??$-4)$?且與?$y$?軸平行的直線上
∴?$2m + 4 = 2，$?解得?$m=-1$?
?$ $?則?$m - 1=-1 - 1=-2，$?∴點(diǎn)?$P $?的坐標(biāo)為?$(2，$??$-2)$?
