I'd like to go to Xiamen from Macau. I read the below 2 different (but, seemed similar) routes, but I still not very sure and hope someone can help me to clarify the actual route.

From the 1st. route, someone mentioned...

"Hi, there is no direct train from macau to xiamen. you can take A21 at the airprort to Gongbei. Then take Bus No.10 and you will get to Xiangzhou Long -distance bus station. There you can take long-distance bus to Xianmen. The bus leaves at 14:00 and the price is 150 yuan."

Question :
May I know A21 is refers to which flight? From where to where? Also, how long the bus travel from Xiangxhou to Xiamen?

From the second route, someone mentioned...

"1. By air
2. You may go to the Gongbei border from Macau downtown and then go to the Qiguan Bus Station to take a bus to Xiamen.
Qiguan bus station is situated in B2, Gongbei border plaza (岐关车站：拱北口岸广场负2层)"

Question : By air is refers to which airline/flight? Flight from where to where?
Also, how long the bus travel from Qiguan bus station to Xiamen? This route no need to go to Xiangzhou - zhuhai, am I right?

Please clarify, thanks in advance.