It feels good that after a series of sleepless challenging nights, finally I've made it 
Yes, I'm now using Arduino IDE ver. 1.8.5 thanks for the info on that.
My next goal is to integrate my DFplayer mini to speak every 7:30 am, 8:30am, 12pm, etc.
I have already posted such as new topic at Arduino Forum > Using Arduino > Audio > Does ADKEYs play specific mp3 file and will not play the next mp3 file?