Can I use a single SMPS instead of 4 separate transformers?
Can i connect 4 nos car halogen bulbs (12 volts 90/ 100 watts each )
  to a 12 volts smps which is 200 meters away ( cable size 6 sq mm
  copper) if yes what amps rating


Yes, you can. But the results won't be good.

Watts = volts x amps, so 100 watts / 12 volts = 8.33 amps. You have 4 bulbs so at 12 volts they would draw 8.33 x 4 = ~33 amps. 

But that only applies when the bulbs get 12V. 6 mm2 copper wire has a resistance of ~0.0029 &ohm; per meter. The round trip for 200 m is 400 m, so the wire resistance will be 0.0029 x 400 = 1.16 &ohm;. If the bulbs had fixed resistance then Ohms's Law says they would be 12 / 8.33 = 1.44 &ohm; each and the circuit would look like this:-







simulate this circuit &ndash; Schematic created using CircuitLab

Which is equivalent to this:-







simulate this circuit

With the same current going through cable and bulbs the voltage would split proportionally to their resistances, and the bulbs would only get 12 x 0.361 / (1.16 + 0.361) = 2.85 volts. So they would be very dim. In practice an incandescent bulb has lower resistance at lower voltage because the filament is not as hot, so they would get even less voltage. This is obviously not satisfactory.  

So what to do? You could run a separate 6 mm2 cable to each bulb, but even then the voltage would drop to less than 7 volts at the bulb.

So you must either use much thicker cable, or a much higher voltage (which needs less current for the same power) and transform it down to 12V at the end of the cable. 400 watts at 110 volts AC only requires 400 / 110 = 3.6 amps, which would drop 3.6 x 1.16 = ~4.2 volts in your cable, less than 4% loss. You could use four 100 VA mains step-down transformers, or one 400 VA transformer, or a 12 Volt DC power supply with at least the same rating. A regulated DC power supply should output constant 12V even if the mains voltage varies.


  also will the bulbs get more hotter than normal


If the voltage is lower they will draw less power and run cooler. In a vehicle the battery voltage is closer to 14 volts when the motor is running, so they might 'normally' get a bit more than 12 volts and run hotter.