SQ835 Feb 2012?
 

My wife is currently booked on a reward flight connecting on SQ835 from PVG to SIN on Feb 25. I can no longer find that flgiht on SQ's schedule after some time in October.

Is this evening flight likely to be brought back to life or should I be going to Aeroplan and asking them to re-book her via HKG or NRT?

Best suggestion call up SQ customer care. SQ has been lately updating quite a lot of it's schedules so better check it out so that atleast you can re-book on another connection.

OK here is the situation...

SQ cancelled the flight she was booked on and rebooked her on SQ833 - 20 minute connection in PVG, so we know that's not going to happen.

The next flight leaves just after midnight which would involve an 8-hour layover and is five hours after SQ835 was scheduled to leave. It would also mean she is taking two overnight flights in a row - who would want to do that?

Air Canada doesn't want to open up a business class seat on any of their other Asian flgihts that connect to SIN, saying it is SIN's problem.

What is SIN's policy on reward flights that get "rescheduled"?

What is the best way for me to get her Business Class reward honoured to arrive in SIN when she wants through some combination of AC, SQ or other Star Alliance flights?

For this, you need to fight it out with Aeroplan.
SQ will not be able to change any of the flights since the ticket is issued by Aeroplan.

Like I told you on the thread on AC's forum, you have to deal with Aeroplan and AC.. and since you're SE, it is AC's duty to accomodate you. You may stick with the same routing but with a long layover in PVG, or travel on another day.

Your alternative could be travelling on another carrier altogether and skip AC entirely.