Is it suitable for 3-6 years age .. and is it cabin approved??
No, definitely not. The seat is small and the stroller gets really hard to steer with a heavier toddler, so for a 3-6yo it will be very tight and for you as the parent - pusher, hard to menuver.
It should fit cabin luggage requirements, but you always have to check with your airline of choice as the allowed measurements are different from airline to airline, and this stroller doesn't have a universal certification.