ReadyNAS RN214 RAID5 disk upgrading

No, your volume is not "degraded", which simply means still accessible, but lacking redundancy.  It's unmountable, aka "lost"  Exactly what I warned you was a likely occurrence when I told you "DO NOT, under any circumstances, reboot the NAS to try to fix this.  The more likely result will be nothing best case or loss of your volume worst case."  There was a chance, assuming you have SSH enabled, that a reboot wasn't necessary.  But now we'll never know.

Each time you've "tried something on your own" you have made things worse and made helping you a moving target.  I understand you aren't trying to be rude, but you are impatient  You want to fix the problem, and you want to do it now. But if you want help, you have to wait for it and you need to heed the advise given to you.

At this point, somebody (not me, I'm not an expert there) will need to analyze your logs and see if you can mount your volume manually, assuming you are comfortable doing so via SSH or Telnet and the Linux command line.  Then, if it is mountable, you'll need to copy the files to another device before you factory default the NAS and restore the files.  There will likely still be issues with some files, which may or may not be readily apparent.  So it's now up to you whether you want to go through the task of trying to recover at least some files (probably most if you can mount it) or just start from scratch now.

And, you may also want to consider a backup plan.  Given Netgear is clearly exiting the NAS market, getting another brand of NAS to become your primary and relegating the ReadyNAS to backup duty could be a good choice.