LDO's Line Reg ,PSRR transfer function
difference between Line Regulation and PSRR is just considering frequency domain?

Yes, they're mostly the same thing: PSRR is a small signal AC measurement. Line regulation  is also a small signal measurement of PSRR at DC (0 Hz).
Line transient response is large signal transient PSRR. Since line transient response is a large signal test and not a small signal test, it has different mechanisms than AC PSRR though. For example PSRR, being small signal, does not test the slew rate and clipping of the error amp, but transient response test do.
Note low frequency PSRR and output impedance of a regulator also include thermal effects. Variations in dissipated power in the pass transistor due to variations in input voltage and/or output current will create a thermal gradient in the chip (at DC) and create different temperature variations in different parts of the chip (at low frequency) which will influence the error amp and the voltage reference. So line regulation also depends on output voltage temperature stability of the LDO.