Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Reset on Frame 0
FIELDLAYER_PYTHON_RESETFRAME0
Parameter: FIELDLAYER_PYTHON_FRAME
FIELDLAYER_PYTHON_FRAME
Parameter: Code
FIELDLAYER_PYTHON_CODE
Parameter: Open Python Editor
FIELDLAYER_PYTHON_OPENEDITOR