Hiro

Corrosion protection is the whole point of stainless.

In general, mild steel is stronger than stainless steel. Exhausts are usually 409 or 304-grade stainless steel, which has a yield strength of ~200MPa (normal mild-steel tube will be 250MPa)

Why would you think that the speedo had been adjusted/tampered? Over-reading is perfectly normal (and in a lot of cases, required by the law) and 4% is well within the expected toleranec range - current ADRs state that speedos cannot under-read (ie the speedo says 95 but you're actually doing 100) but can over-read by up to 10% +4km/h (so you can be doing 100 but the speedo can read up to 114)

It could be something else in the starting circuit too (relay, battery, wires etc). Unless you can prove that the flywheel is warped without removing the gearbox I'd be checking everything else first (otherwise you could be spending an arm and a leg on labour for something that could be completely fine)

Pretty sure the hatch light is purely for reverse, and the red is just a reflector. The rear corner lights are combination lights covering both brake- and tail-lights (two filaments in a single bulb) along with the indicator. EDIT: Confirmed when I went shopping last night. Parked behind an Ascent and left the carpark behind a Levin (both pre-facelift) and neither had any red bulb in the hatch light (and both had combination brake/tail-lights in the corners). It's different on the facelift models where they have a single-filament brake bulb (in the corner light) and LED light-pipes for the tail-lights in both the corner light and the hatch light.

Properly called a door side moulding but commonly just called the "rub strip"

How do you know it's the flywheel/ring-gear and not just an issue with the starter motor?

106.1 is almost certainly for the 6-stud PCD

No, 'I' and 'O' are not allowed in Australia either (neither is 'Q'), it is just that some systems have the smarts to normalise them to 1/0 as needed when you type them. https://www.ppsr.gov.au/vin-vehicle-identification-number

TRD came in both helical and clutch-type, Quaife is helical, Kaaz is clutch-type.

35,000k a year is pretty significant, not taxi or travelling-salesmen level but still higher than your average commuter (although since you're in the NT things could well be different). Has it had a hard life or just open-road cruising? Former hire-car (and hence thrashed by renters who don't care)?

Yes that is a Sportivo, although there were non-Sportivo models also built in South Africa (AHT) so you can't just use that alone as a reference.

Where are you "checking" the VIN? If you're trying to find things in online parts catalogues they won't show up as they don't tend to cover the Australian-built cars (ie those that start with 6T). Also, in that VIN you quoted you put an 'O' in there, VIN numbers cannot have the letters 'O' or 'I' as they are too hard to distinguish from the numbers '0' and '1', so that'll cause problems with any VIN checker you use regardless.

Is it a petrol or hybrid model? The petrol has a iCVT where there is a physical first gear (for better off-the-line performance), I wonder if this judder is related to the transmission switching between the CVT and the launch gear.

Check along the bottom of the door skin for drain holes, these are most likely clogged (just poke them out with an old coathanger). You'll always get water in the door as the window tracks cannot seat perfectly, but if it drains properly then you shouldn't have any problems (the electrics inside the door are either sealed or separated from the water by a plastic sheet/skin)