DFPlayer Pro - A mini MP3 Player / how to play in order

Q1. 

/**

* @fn playSpecFile

* @brief Play file of the specific path

* @return Boolean type, the result of operation

* @retval true The setting succeeded

* @retval false Setting failed

*/

bool playSpecFile(String str);

what is the specific path? 

please explain in detail.

I changed the name of the music file . like 1, 2, 3, 4, 5…

playSpecFile("1");  → play 1.mp3

playSpecFile("2");  → play 1.mp3

playSpecFile("3");  → play 1.mp3

but it played only one song.

Q2.

/**

* @fn playFileNum

* @brief Play the file of specific number, the numbers are arranged according to the sequences the files copied into the U-disk

* @param num file number, can be obtained by getCurFileNumber()

* @return Boolean type, the result of operation

* @retval true The setting succeeded

* @retval false Setting failed

*/

bool playFileNum(int16_t num);

The numbers are arranged according to the sequences the files copied into the U-disk

I copied the file in order 1,2,3,4,5,6,7…

but the file number is different 1,2,5,7,9,11,12…

how it happened?

Q3.

I just want to play the music that I want in order

what is the best way to do it?