1. Reading the DIY ATF Service http://www.ozhonda.com/forum/showthr...and-ATF-Filter. He uses 3/8 Magnetic inline transmission filter. Is that an alternative part to the Honda part 25430-PLR-003?
An aftermarket part yes.

The aftermarket part is bigger in capacity, but it wont fit the clip where the filter is secured against.

2. From reading the product information on both Valvoline Maxlife DEX/MERC ATF and Penrite ATF Multi Vehicle FS, it has a note regarding not to be used for DSG and CVT. Does this note apply to the CL9 Euro?
No, CL9 accord euro does not use CVT or DSG.

Is one better than the other?
that I dont know, but since Penrite is an local company, I'd give them a shot

theres this full synthetic Penrite Multi vehicle ATF:
http://www.penriteoil.com.au/product...d_products=336

^^^ once my redline d4 run out thats what I will personally use.


3. When you said 3 x 3 - do you mean change the transmission fluid 3 times (every 10000km) with the same oil because each time I drain the transmission fluid I can only get 1/3 of the fluids?
Fill and drain 3 times in short succession

so:
1. drain, fill, drive for 10-15 minutes,
2. drain, fill, drive for 10-15 minutes,
3. drain, fill, done

thats a 3x3, meaning 3 litres, 3 times.
just make sure your drive in between contains a stretch of highway.

4. When do you actually change the filter at the beginning of the cycle or at the last change?
doesnt matter.