On 14 January 2019 Microsoft stopps support Windows 7. Is it necessary to go to Windows 10 now (in Jan-March) or mayby there is some open source community who provides programs which can secure Windows after Microsoft stops it?
Yes, if you want to keep using Microsoft Windows, otherwise there are various alternatives such as different Linux distributons, macOS or BSD.
As Windows is not open source software, it cannot be given security updates by anyone else than Microsoft. If you wish a precedent, look into the situation of Windows XP.
No, it is necessary to migrate to a supported and maintained operating system. As @Mikaela stated, depending on your needs and use cases, there are alternatives. Even Windows 10 comes in different variants.
Don’t install additional software while assuming that this software somehow disables OS-level security vulnerabilities. Migrate to a supported and maintained operating system.
Some sort of extended support may be deployed by 0patch
Anyway, upgrading to Windows 8.1 instead of Windows 10 is an option to consider.
Is it worth to upgrate? It seems Win 8 has only one year more than WIn 7 before support ends.
Do you think that running Win 7 after Jan 2020 in Virtual Machine is solution which could work for some time (due to higher safety caused by VM)?
Well, actually the end of extended support for Windows 8.1 is January 10, 2023, so three more years to go.
I think it’s worth the upgrade.
Unless you absolutely need to use Windows, I would highly suggest using Linux. It’s an operating system that actually respects you, and is fully open source.
Another option is to start dualbooting running some other OS on a different partition alongside Windows 10.
My grandmother ended up to this solution yesterday as upgrading Windows 7 to 10 was being too painful on ~10 years old computer (her word, didn’t check) and as everything was backed up on external HDD, I finally format the disc and installed fresh Windows 10 on it which went better, but it didn’t accept Windows 7 product key.
She was also a bit curious towards Linux, so in Windows + X / disc manager I shrunk
C:\ and installed Kubuntu 18.04 LTS (my Debian iso didn’t want to load some package and Kubuntu may be a bit more user-friendly and didn’t want to install 20.04 Development Branch while it’s coming out in ~three months too.
Her usage seems to have been moving towards tablet, so I am not sure how much it matters which OS she is going to use, but if Windows 10 gets nasty on missing product key, she has the option to use Kubuntu.
I picked Kubuntu as I think KDE Plasma is closer to how Windows looks and otherwise fully featured desktop environment, but I have also been told that Xfce is another good choise migrating from Windows 7 as long as you move the top bar to the bottom.
How about Linux Mint for your Nana?
I am not sure if you can use it on a tablet.
Like others have said here already, it is not necessary to go to Win10, your system will continue working however, you will no longer recieve security updates for any newly discovered vulnerabilities or exploits.
Having said that, if you value a secure system, I would recommend that you upgrade to Win10, but better than Win10 is Linux (in terms of security). Dual booting allows you to keep your Windows and install/run Linux on the same computer.