@2Rebecca when Yolanda left for the first time, she was shown into an empty flat, having been directed there under the impression it was occupied (she had planned to visit Syed/Hashu) and she saw Emma on the tv in there, telling her to go back to her own flat and choose a cloning victim!
Wrt the others mostly not thinking the clone could be Yolanda, they saw her goodbye message and although the circle has many twists (people have stayed on before), I think it lulls you into closure, so you do think "right, next"! Even knowing that the circle plays tricks, they have a lot to keep track of and she committed to being someone else and wasn't being herself to begin with either, so she possibly was quite easily forgotten beneath Tally. People who stay on usually commit to another identity so even if they don't ring true in their disguise, you wouldn't necessarily guess exactly who they really were with a whole world to choose from. Players seem to focus on what's in front of them and on broad clues - that doesn't sound like a man so it must be a woman being deliberately laddy, that sounds too much like a woman so it's likely a bloke trying too hard, that nurse knows nothing about first aid so whoever that is they're probably lying and not a HCP, how can that 68 year old not know who Maggie Thatcher is, they're probably a young'un etc- rather than hunt for a specific person.
Wrt the building if the "circle" on the front is accurate with the balconies within it all lit up, I always thought thats where they were. So it would be 9 apartments + hangout space over 4/5 floors and they're neighbours but with possibly stairwell breaks between next door neighbours so they're not back to back and good sound proofing! My best friend used to live midway up a huge block in Elephant and Castle and she never had any complaints about massive, loud after parties coming back at 1am going through til 5! I wonder how easy it will be for them to reuse flats this year with quarantine though. I'm guessing starting contestants/later incomers have all been bubbled etc but are cleaning regs stricter? They have reused flats before, I think.