Watchface compiled with 4.2.1 cannot read bodybattery on a real device

The question is: why did they force in new devices minimal sdk 4.2.1? Is it connected with something (e.g. symbol in api was changed? vm was changed?) are or only to force using 4.2.1?

If you check about on a device, you'll see the CIQ version of the VM. It's something they generally don't state when new FW for a device is announced.

I could always see ciq ver in system|about (now 3.4.0). What do you mean saying  "CIQ version of the VM", is the same?

Yes, the VM on the device is 3.4.0.  So System 6.

But I've asked, why new devices require 4.2.1 sdk?

Because the new device have API versions of 3.4.x or 4.2.x and the SDK needs to understand that. The 4.2.1 SDK does.

Only if you use system6 features. If not, then you should be able to use older sdk

Yes, so in previous releases, only new devices had "current" sdk version. Now after 4.2.1 was installed f6 need it but when I don't  to want to use any s6 featured why they force me to use 4.2.1?

In the device file the System 6 devices (the ww ones) have 4.2.x 3.4.x as the api level and an SDK that understands that is need.

Why are you worried about using 4.2.1?