Can reversing AC polarity of one of two adjacent LED bulbs reduce overall flickering in a room?
Can reversing ac polarity of half of the bulbs in a chandelier bring the flickering out of sync (out of phase) so that half of the bulbs are ON while the others are OFF?


No. The bulbs will use a full-wave rectifier so that the LEDs are powered on both positive and negative polarity of the mains. The result may be flicker at 100 Hz  or 120 Hz depending on whether you are in 50 Hz land or 60 Hz land.


  I did some experimentation with a 5 W bulb, a testin socket and the phone's camera after removing the defusing cap and zoom to the LEDs but the result was not what I expected:


I have no idea what a "testin" socket is. If it's a brand name then it should probably be capitalised.


  .. the light was not exactly blinking but moving in a line from side to side and when the socket was flipped instead of reversing direction or just stay the same the light just flicker without the first pattern.


There isn't enough information here. Moving from side to side in what? The video? In what orientation was the camera running? What camera, etc.