Okay, I'll try to answer the questions that you've posed.
The start of care date is the same date as the admission date is the same date that the first billable service was rendered.
Episode of care = certification period = 60 days.
Recertification is to provide another 60 day episode of care. A recertification OASIS assessment must be completed between days 56-60 of the episode for compliance.
Plan of care = Form 485 = nursing care plan = physician-ordered plan of care. Your agency may also require a nursing diagnosis care plan but CMS does not. Check your policy and procedure manual or ask your director of nursing/clinical services.
Reimbursement is the amount of money that your fiscal intermediary pays on behalf of Medicare based on the OASIS assessment, number of therapy visits, and timing of the episode of care. Reimbursement is determined by the HIPPS code. There is a recent thread in this forum regarding that, take a look.
If you are asking these questions, you should not be submitting a claim. Hopefully you are working for an agency that is submitting claims. You must complete a visit note or OASIS assessment for each visit that meets the criteria for skilled care for it to be billable, as well as being within the ordered frequency.
Private insurances and/or HMOs (including Medicare Advantage plans) are rarely as lucrative as straight Medicare. They put restrictions on the number of visits allowed and require increased documentation and authorization for further visits that may not be allowed.
Best place to start learning about home care is directly from CMS.