I downloaded from http://seeds.dero.io/alpha/ the wallet supports: dero_windows_amd64.zip and dero_windows_x86.zip, (no matter). Up to now, I have already (existing) DERO wallet which is not synchronized anymore. When I run, for example, dero-wallet-cli-windows-amd64.exe, then after "open existing wallet" option, I was asked about the wallet filename (default wallet.db). Unfortunately, I don't find the wallet.db file anywhere in my previous user-friendly skin DeroWallet_Win64_v0.0.3 folder.
Does it mean that, unfortunately, I completely lost all coins what I have in the previous wallet and I have to create a new fresh wallet in a new command-line skin? Or I can somehow recover and return my previous mining founds?
You need to select the option, "recover wallet using recovery seed (25 words)" from the wallet-cli menu. You should have written down your 25 word recovery seed when you first created your wallet using the old wallet-cli, but if you didn't there is a command to get the seed from it (I don't remember the exact command and I already deleted the old wallet-cli).
See my previous post where I went through much the same thing as you: https://bitcointalksearch.org/topic/m.33402693
Pipe down man ffs, it's a few devs working their nuts off trying to get this straightened out for everyone.
I'm sure all the boring code you want to scrutinize will be available in good time.
Give them chance.