if lose for a few times opponent will suggest that in first turn, only pick and do not play. but opponent's second turn will surround my bottom right 7 gem which is clearly bad for me.

i found an old post linking to a youtube video about m3, and at that time the opponent only played 2 cards per turn so bottom right gem didn't get surrounded in 2 turns, and 47 and 61 was swapped so 122 was more useful. 

m3 seems impossible for me :(

You're right, that hint is out of date. I will remove it.

I was able to beat M3 (16 to 12) by playing 61 and 2 on the first turn such that only one of them got frozen.

playing the large stones instead of just factoring them is very important in this fight