Yes, the Omega2 and Omega2+ will be compatible with the new OpenWRT 18.06 based firmware that is on the Omega2 Pro. This firmware will be released sometime after the Omega2 Pro ships. If you would like to test it out yourself beforehand, our build system is available on GitHub and can be used to build the firmware.

The current price is crowd funding promotional price, expect it to change after the campaign is complete.

Regarding your question about kernel mismatch issues, this is a more involved topic:

Installing kernel modules with opkg: To ensure that all installed kernel modules are the exact same version as the device’s kernel, opkg has safeguards that only allow it to install kernel modules compiled by the same machine that compiled the firmware. I presume this is done because installing kernel modules into an older kernel would likely be pretty disasterous. The OpenWRT 18.06 based firmware runs kernel version 4.14, and there is a large number of kernel modules that we build and make available in the Onion package repos. If that doesn’t suit your needs, the build system can be used to compile additional kernel modules. Updating to a newer kernel requires a full firmware upgrade. I presume that OpenWRT won’t move to a newer kernel version until the next release. We’ll cross that bridge when we get to it.
I hope that answers your question

Yes, the designs of the Omega2 Pro are available here: https://github.com/OnionIoT/Omega2-Pro
Nice detective work :)

As you’ll see in the schematics, the LiPo charger IC is the TP4056.

Regarding the two photos, the one with the sticker that says "Omega2 Pro" is an early prototype. The other photos feature a unit from our 60 unit sample run. This is what the production models will look like.
The Omega2 Pro design is based on the Omega2S+, there are no differences between the Omega2S+ used in the Omega2 Pro and the Omega2S+ modules that are currently available to be purchased from us or Mouser.