As the battery is the same as on Gen2, only difference is rockguard and charging port design, it should be easily removable. Maybe shops are referring to Levo SL which require more effort to remove the battery...
I upgraded to PG1230 cassette, X01 chain and GX AXS derailleur, one of the best upgrades I did on the bike, now after about 3kkm took quite some beating (also crashed and bent derailleur hanger which had to be replaced) still works flawlessly ...
I had exact same setup before upgrading to Eagle so I'm pretty sure there is no spacer needed behind the lagest cog in this setup. Maybe your end nut on the axle is not tightened enough so freehub body has some free play together with a cassette?
Are you sure there is so much difference in weight? Have you weighted both?
Because according to specifications PG-1210 is 630g and PG-1230 is 615g ...
SX and NX Eagle cassettes are very similar, I dont know any particular difference other than NX being about 15 grams lighter and cost a bit more, both are all steel and both have Shimano HG freehub body. Get whichever you can find on stock ...
Yes, they are all designed like this. Why? Reread my previous post.
Same way you have to press brake pedal with any car with automatic transmission only to start the engine ... little safety features to prevent majority of users do stupid/dangerous things ...
Sure Specialized software team knows very well how to make TCU2 compatible with whole gen2 and gen3 models, both generations are based on the same platform. They just decided to put some extra effort into it to make it incompatible. For obvious reasons.
I think it can go down for about cm, I'm pretty sure it cannot be slammed it all the way in ... It comes with pins with which is possible to shorten the travel by 1cm increments ...