Questions about multi-area ospf

Hi, me and my university group are working on our networking design project. This is the topology where ospf is in question https://i.imgur.com/DtkQbZO.png. We're unsure whether we setup multi-area ospf within the red circle or the blue circle

another note on router_inverness_1 the left of it isnt configured yet as we're still waiting to sort the firewall. we were supposed to have a meet this week but covid has our country on lockdown so we've had to postpone. slightly related to this, can i add a network later on onto ospf?

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Any information helps

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Thanks, david