Yes chain must be also 12sp, I have installed X01 Eagle chain shortened to 120 links, original chain was 116 links with 11-42t cassette and 32t chainring. I now still have 32t chainring.
Yes, you have Shimano freehub. You can install PG-1210 or PG-1230 cassette without replacing freehub. I have also upgraded to GX AXS which works perfect.
I don't think we are on the same page so I'm attaching reference section image of rear boost hub. Purple/blue is freehub body (although not XD but Shimano version in this image). The red part is hub axle which may be the one they need to replace and which is out of stock, it should have 12mm...
Not (necessarily). With higher price you will mostly only get lighter components... But since there is a shortage of components (the cheaper the component less likely it will be in stock) you may have to pay a bit more for what's available to get you back on trails ...
It looks like you have 11-51t 11sp cassette, you can replace it with Deore-SLX-XT-XTR depending on availability and your budget. For the chain look for cheapest 11sp chain which have same or more links and then you shorten it to suit your drivetrain, easiest way is by comparing length...
Just because it shifts silently and nicely under load it doesn't mean it will not eat up the drivetrain way prematurely compared to if you shift with mechanical sympathy ... Keep in mind that manufacturers are still the ones which want to sell you as many parts as possible ...
1500 miles is very low for a cassette. Mine 12spd chain should survive up to around 1500 miles until 0,5% wear and I normally replace 2-3 chains per cassette. I also have this thing - the Mechanical sympathy.
I expect no surprises regarding equipment, I guess it will be more or less same as on 2021 models, beside new alloy frame with adjustable geometry, new charging port (which apparently has quite some problems with breaking away doors), 2.2 motor (still not proven to be more reliable than previous...
IMHO chain cleaners/degreasers are just for sucking money out of your pockets or if your main goal is to have a perfectly clean chain - which doesn't necessary mean it will last longer. I like to keep it simple and don't wanna put much time and money in chain maintenance. I just lube the chain...
Yes, heat maps are shown in record mode for me (non-subscriber).
I do believe Strava will keep this feature free for a while (to addict as much as possible non-subscribers) and then they will make the feature available for subscribers only ...