SQ/VS rtw...

[aerosmith]

Don't forget the additional surcharge of US$500 for the EWR-SIN sector due to A345 aircraft.

[Savage25]

Only one stopover per city allowed.
Unlimited transits per city allowed.
MPM 29,000 miles - you can buy additional 1500/3000/4500 miles for 150/300/450 USD.
If you can fit SYD into the MPM, then it would be valid.

HKG-SIN-LHR-BOS//EWR-SIN(stopover)-BKK-SIN(stopover)-HKG
would not be valid as only one stopover allowed in SIN. If you can make one of those a transit, then you should be fine.
Also, I'm not sure if EWR-SIN is counted as transpac or transatlantic for the purpose of this RTW or whether that matters at all

[SQflyer]

Hi I was just wondering if anyone had the fare rules for this particular rtw...and whether this particular routing would be valid ex..HKG...HKG-SIN-LHR-BOS//EWR-SIN(stopover)-BKK-SIN(stopover)-HKG??? Would sydney be valid or any other sidetrips how many times can SIN many transitted? it costs quite a bit more than the the great escapade fare but had the advantage of allowing u not to fly via/ the southwest pacific........at 42, 000HKD in business I think its still relatively reasonably priced....
Thanks