there are more differences in implementing an IC in FPGA and in ASIC.
using FPGA, we can use the available resources or blocks in it. but for ASIC implementation we need to add all the blocks like multipliers,memories,PLLs etc.
implementation in ASIC, can be for large chips & high freequency chips.
but if the area is large, we need to split the logic into multiple FPGAs, so operating freequency may reduce.
after imlemnting in PFGA for validation, we will go to ASIC implementation.
for that, we need to change target libraries to ASIC vendor libs. & need to resynthesize with that lib, then P&R, then tapeout.