Did you download the insider ISO 22454.1000 ?
If yes did you create the installation media on a FAT32 USB Flash ?
You will need to rename one file in the sources directory to bypass some of the checks and then you can get to this point which you can read and accept at your own risk, assuming you are still in R.P. channel right now.
Once the upgrade is done while in R.P. you can then force it to Dev by hacking the Reg.
Once all is done and you are at 22454.1000, the next W.U. for next build updates will still need yet another trick to bypass some of the checks.
We can talk about that after you get there.