I don't know if Electrolux makes their aircond themselves. I heard from a friend that for their water heater, Pensonic is their OEM

What I thought too. The last step should be the turning of the valve at the outdoor unit to let the gas into the system

Yes it takes a while but not that long. You can feel the cold air blowing mere seconds after switching on even on a hot day

Depends on your usage. If switch on for a long time get an inverter

Panasonic Non Inverter already uses the new gas, R410A now if you want to continue using it long into the future, but the price is at RM1k, so more expensive than the Mitsu. But don't worry too much about using the old R22 gas lah Considering the gazillion aircond units still using it here, rest assured that the supply will still be around for quite a while

Some might not benefit from the inverter function. As an example,tthose who regularly set their aircond to ice cold, (Below 20c) will not benefit from using inverter as the compressor will run at full power all the time trying to achieve the set temp. For these people they are better off buying non inverters

Well. My parents (specifically,my mother) likes it cold like that. The aircond in her room is the correct size and provides good cooling. Personally for me i think 23 to 24 c is enough already to feel comfortable. But she likes it to be under 20c. Only then she feels comfy enough. So what to do...

True that. But I would say the key points are the temp and duration. Main advantage of inverter is the variable speed compressor. Once it reaches ur set temp it will slow down. So if you set the temp too low,it will take longer to reach that temp, hence the compressor will take longer to slow down. Inverter starts to save electricity once it has slowed down the compressor. For example like me, on average my room temp is about 29c. (I have a clock with temp and humidity reading) I set my aircond at 24c. It can reach that temp in about half an hour. So from that point onwards I save electricity already.

That is one of the weaknesses of an inverter unit. The printed circuit board (PCB) if not sealed properly can be damaged by moisture or insects,whereas a conventional unit is not prone to that problem. That is why the emptiness of a conventional unit that u mentioned is kinda an added advantage

There should not be any gas coming out of the vacuum pump. Coz the function is to vacuum all the air inside the piping prior to getting the gas inside the system

If just a bit leaked out don't worry. Coz they have extra gas in the system. Enough for 15m piping