Flying AF ticket on SQ metal, can I earn VA status credits?

Flying AF ticket on SQ metal, can I earn VA status credits?

I am flying Mel to CDg via SIN on SQ and then AF return in J. The ticket is issued via AF. I am travelling with wife and 2 kids. Can I associate the mel to SIN sectors, before departure, to VA to earn status with them( if so how many status credits will I earn for the 4 of us I believe 480 one way). My plan is then to associate the remaining AF sectors to flying blue, not that I fly AF much, to collect some FF points with them.

You haven't said whether the Singapore Airlines flights are booked on an SQ or AF flight number. If the former, yes, you can earn points and status with Velocity. With the latter, nope, no Velocity points/status on an Air France flight number.

its the latter

sorry the former on info from agent, AF and SQ

SQ 238 and SQ 227

Then you're good to go for earning VA points / SC on those sectors. 

can I associate the AF sectors to flying blue after the flights, so that the sq sectors have already been taken by VA?

How many status credits will I get per  pax? i believe 120 per one way mel sin?

One way, in business, on SQ, SIN to MEL Nets 120 SC with Virgin Velocity. Yes.