When a power source is AC (Alternative Current) one is a phase and the other is neutral.
AC stands for alternating current, not "alternative" current.
The neutral is so-called because it has been neutralised by connecting it to earth / ground.
simulate this circuit – Schematic created using CircuitLab
Figure 1. Two AC supplies.
(a) has no ground reference and so neither line has been neutralised and neither can be called "neutral".
(b) has one secondary connection connected to earth and so that conductor is neutral and the other is live.
Does phase and neutral lines are changing their polarity over time or on phase line voltage and current up and down sinusoidal form?
Your sentence is rather confused. Neutral has very little voltage on it and can be considered to be at 0 V for basic analysis. The live wire voltage oscillates in a sinusoidal wave from peak positive voltage to peak negative voltage.
If it is not changing the polarity of how rectifiers work.
You can't "change the polarity of how rectifiers work". You can, however, edit your question to clarify. If you do that we can try and help you further.
simulate this circuit
Figure 2. (a) The full bridge rectifier. (b) When the AC is positive (as defined by the secondary dot) D5 and D8 conduct. (c) When the AC is negative D11 and D10 conduct.
No matter which polarity the AC is the diodes steer the current to the positive output.