From the subsequent sub links, the licence you bought was bogus, so your install is still not a legit copy - did you rectify that ?
Ideally when you are subject to frequent power outages it would be best to buy an UPS, but with trade restrictions this could prove difficult.
If your Win 8.1 licence is now genuine then you can contact MS and ask to have it reactivated, but I don't think there are any restrictions on reinstalling the same OS onto the same machine and using the same product key.
The problem arises when you try to install it onto another machine or when you have had to replace the motherboard, as it's the motherboard it takes the "fingerprint" of.
Frequent power outages can take their toll on computer hardware and some computer vendors have a decent diagnostic program to check out the hardware.
If you let us know the make & model of your computer, then we may be able to find the appropriate diagnostics if your machine is an OEM one.
The frequent power outages could also have taken their toll on the RAM, so doing a memory diagnostic test may show up something, but if you have more than one RAM module fitted then it's best removing and running the memory test on just one module at a time.
Open a Command Prompt (Admin) and enter chkdsk
This is a read-only mode but will report any file or HDD problems and recommend remedial action where necessary.
If the chkdsk reports any bad sectors then back up your personal stuff and run a chkdsk /r
This won't repair the bad sectors but will repair system files where it can and if the amount of bad clusters is only small, then you should be able to continue to use it for a while longer, but create full external system images in preparation for a complete fail.
If the chkdsk reports no problems then enter sfc /scannow to see that that reports.
If the sfc /scannow reports it is unable to repair some files, this could be the result of recent Windows Updates (if you can get any) or genuine corruption.
Regardless of whether sfc finds anything, you can also run this command - dism /online /cleanup-image /restorehealth and see what that reports, but hardware problems trumps software so you need to determine if the outages have caused hardware problems.
If you have resolved the problem of having a legit licence, then further help can be given.
