even 10 sen also saving.

Inverter one has at least 10 years warranty. Non-inverter usually much shorter as far as I can remember

That can easily buy and DIY replace.

My air-cond even on during sleeping hour also reduced by about RM30 per month.

The reason for different copper size has nothing to do with inverter/non-inverter. The difference in size are due to:
1) Different refrigerant use.
2) Different power. You can see the after 1.5hp, the pipe gets bigger if not mistaken.

Inverter part the difference is only the control board. The rest is the same. Well. In my experience using air-cond, never had any faulty board. The main problem is after years it's getting noisier because the rubber insulator deteriorate. The replacement rubber (usually 3 pieces) on my 1hp air-cond I bought only around RM8 and I replaced them less than an hour. Now it sounds like new again.

I think when I replace my old non-inverter one with new one, my electricity reduction is about RM25~30 perhaps. Probably part of it due to more efficient compressor? I don't know. I used air-cond only during sleeping hour

No reason for that except you probably spend same amount like non-inverter one but get faster cooling

Same concept because the inverter part is about how the compressor in controlled. Both fridge and air-cond same cooling method.

For fridge, if your fridge is not open/close too frequent i.e. less loss of coldness, you probably don't much difference in power usage. That I can say for sure. If many people use fridge like many children in house then inverter is good. The non-inverter use of electricity is more because the compressor is shut off totally once the temp is reached. The current surge during each re-start of compressor makes it high power in use. The non-inverter one compressor cycle between full power on and totally off. The inverter one keeps compressor running but use less power when it is already cold. That is the difference.

It is the same actually. The air-cond is chilling room by removing heat to outside of the room. In fridge case, the inner side of the fridge is the room and the heat is removed to the outside of the fridge cabin which is into your house unfortunately.

If you asked me if it is worth it an extra 1k, I'd say it is not worth due to additional cost for inverter board compare to regular board probably just RM100~200. The compressor still the same compressor but the longer warranty is due to there is no in-rush current to compressor during operation thus it is very unlikely to get the coil burnt. The 1k extra is very much due to inverter is current hype.

As I mentioned before, it depends on how much coldness loss inside your fridge. The more frequent the fridge door is open/close in a day, the more time the compressor works. How much electricity saving related to this factor. If less open/close the fridge door then the difference is saving probably negligible.