I need to change two tyres (got crack already), while keeping the newer and still usable tyres (currently mounted on front). I... don't really know what model the tyres I'm keeping are (they're continental for sure) as I'm noob and this car is 2nd hand so I do not have the details.

My Subaru XV 2.0i is AWD. When changing a pair of tyres, how should I handle the rotation? Think I read before that AWD should rotate front-to-back as well as side-to-side unlike FWD?

In terms of brand, from survey I think in mid-budget range got Toyo CR1, Hankook K135, Falken Wildpeak, Continental UC6 (I think this one costs a bit more than the others?). General vibe I get is that Toyo is reliable and no fuss, so leaning towards that. Any advise on this? The usage is primarily highway driving (commute roughly 70km) and my priority is safety and durability over long time (so not looking for those 'nice' tyre which wear out quite fast).

Final question - tyre shop tend to have reviews which are all over the place (both on FB and google maps), how do I identify one which is reliable? I don't mind if its not the cheapest, good workmen should be paid for their expertise, but many comments in this forum are like "alignment they will just raise and lower your car then charge you" and similar vibe. My area is Subang Jaya if it helps.

The solution is simple, every 10k (during service) rotate the tires and do alignment you will have all 4 tire balance in wear.

You can ask for tire turing or shaving.
If other 3 tires still new you can still gamble with 1pcs replacement.
Besides that, most local CKD Subaru also got spare tire to use.
For short term should be no issue. 

https://www.consumerreports.org/cars/tires/...es-a4235415952/

FYI, modern 2WD rides with Vehicle Stability Control/ABS also need proper tire condition as tire size & wear will impact the braking performance. Dont believe, go read your car manual book. I personally read Toyota Corolla Cross manual book before and it also mentioned about it under 6-3. Do-it-yourself maintenance. Under tire session.

Do not mix tires of different makes, models or tread patterns.
Also, do not mix tires of remarkably different treadwear.

Most feedback only need to replace at least 2pcs for FWD per axle, that will be good for those older vehicle with not much safety features. Even 1pcs replacement is not a good idea for modern FWD rides nowadays.

1.6mm still very less, if you did not align & rotate the tires one or 2 round confirm will over the limit.

FYI Subaru AWD tires' tread depth difference for all 4 within 2/32~3/32 = 1.6mm~2.38mm.

Not sure where you get more stringent in term of treat difference allowance.