1. SVC Vs DVC? pros n cons
None, just wiring options on a DVC. Performance is/can be the same or better either way.

2. what is single magnet and double magnet? izit related to SVC or DVC?

Single or double stacked magnet, doesn't matter as long as the sub sounds good. Strength and quality of the magnet matters more.

3. how to determine the good specification of a woofer?

By looking at the graph of what it can do. Other specs doesn't really tell you anything but help you find the right ancillaries to match it with.

4. how to match amp with proper specification of a woofer? eg: impedence, rms

Find an amplifier that can handle the specified impedance. The sub will have a safe operating power range. i.e 30w - 500w. Pick a good amp that has a true power rating of anything in between. If you're into SPL, you may want to find something that is on the upper range of the power scale or a little more wouldn't hurt.

5. how to fully optimize woofer performance?

Build a proper enclosure for it (right size, non leaking and suitable for the purpose). A sub does not perform miracles by itself. Building the right box, setting the right frequencies and feeding it clean/wholesome signal will give you more enjoyment that just buying an expensive sub and not knowing what to do with it.