The bulk of your questions can be answered by reading the appropriate standards. In this case, it would be the ISO 9141-2. There are dozens of timing parameters that you need to know to build an OBD simulator, do you seriously intend to create a post and ask for each one of them? Yes, the spec is not free (it's ~$30, IIRC), but you need it to do your project. Save your lunch money, buy the document, and stop wasting bandwidth with RTFM-type questions.