Ok, with no wire modification made from #1 post. I successfully made the OBD-II adapter talk to the Arduino today. The led on the ELM327 flash when I power up the Arduino. It means Arduino talks to the ELM327. But all dates are zero on LCD. I think I need change the header from elm_init function to make it work.
I will keep update for my work
4 and 5 questions still need answer. Would anyone can?