I understood. I'm from the Russian popular (known) site. We did not have such reports today. Update to all came normally. I think that you needed to wait longer. Antivirus monitors the change of all files, including the process of updating the system. Therefore, it may take longer to update.
No idea, but could be it due to the geographical area, IP, etc? Seen that Kaspersky free doesn't provide English version, I assume some limitation may exist.
From your profile I see that you do not live in Russia.
No way. Only temporarily disable real-time protection. When the real-time protection is disabled, the update is still not installed ? If so, install the update on the link above. An error with the update may not be associated with the antivirus software. The solution is still the same, update offline.