An update to my original posting:

I called to confirm seat selections on the EWR-SIN-EWR flights and............

I was told I cannot obtain guaranteed seat assignments.

All SIA can do is put a "request" into their computer for the seats I want. Although the agent said usually those "should be" your seats, she couldn't say anything more than that. With respect to the bulkhead seats, rows 31 and 34, those won't be released until day of the flight - I guess not that unusual. However, we fly a bunch and I'm not sure I've ever had the situation where we couldn't obtain seats certain at the time of ticketing. Is this normal for SIA economy?? Is it worth calling again and try a different agent?

Concerning the change to all business on these EWR non-stops, I asked the agent about that. She said no decision "had yet been made" and, in response to my question as to what would happen to passengers already ticketed on the flight, she said they would remain on the flight, even in business. In contrast, if you weren't ticketed at the time the conversion is made (announced?) you would be out of luck. Our flights aren't until next year and I had thought I might wait a bit to purchase an additional seat we may need but, perhaps this argues for purchasing now? Thanks again.

PS
They did have rows 32 and 33 available in Exec Economy. However, because we want two sets of two seats (i.e., rows 32 and 33 window and aisle) my fear was that row 33 might not recline fully because it backs against the lavatory. Does anyone know if this is the case? Thanks