I94 return date for B1/B2

In the DS160 I have mentioned duration stay as 4 months (just to be on safer side), but I do intend to stay for 5-6 months. My B1/B2 visa interview is in a month. Now I’m hearing I need to book return flight tickets to show to the visa officer and POE officer. So do I need to book a return flight matching the 4 month duration on the ds160? Also, will the POE officer give my i94 return date exactly as the date on my return flight tickets? If the POE officer gives an i94 date matching to 4 month stay, can I overstay that date but leave the US before the 6 month limit?