As per subject, can I do so? If yes, what is the supported DDR? DDR2? DDR3? and what is the supported speed?

we would not encourage you to solder RAM chips. But you can read info from the memory chip.

if you just purchased CCR1009 - some resellers may had exchange it with additional money to CCR1016.
anyway its less risky(in both senses), and less expensive. and plenty of modules to pick (instead of 2GB DDR3 SODIMM with 10600 speed, installed usually)from.
another point for that way - extra-performance of CCR1016 CPU, which you may not need today, but may enjoy bit later.

p.s.
with incoming metaROUTER features porting to Tilera arch branch of RouterOS - consumers appetits may just grow, shortlyafter.
thats why i consider picking sodlered memory on CCR1009 nice tradeoff, but not amount of it. if there would be RB1009 equivalent with SO-DIMM slot(filled by marginaly-sized SO-DIMM by default. or empty at all and used instead of soldered in case of installation, during pre-boot init)there would be some consumers for it too.