"Webpage not available" for some webpages but not all
Let's check the supported HTTPS protocol versions of the sites you mentioned.


https://wiki.archlinux.org -> only TLS 1.2
https://github.com -> only TLS 1.2
https://jisho.org -> only TLS 1.2 
https://google.com -> TLS 1.0 TLS 1.1 TLS 1.2
https://leo.org -> TLS 1.0 TLS 1.1 TLS 1.2
https://wikipedia.org  -> TLS 1.0 TLS 1.1 TLS 1.2


Do you see the pattern? From my perspective I would assume that the used browsers use the old outdated web engine of your OS which does not support TLS 1.2. 

My suggestion would be to install the Chrome app and use it (and may be even set it as default browser engine - was this already possible on Android 4.0?). 
Chrome includes the latest SSL/TLS libraries with TLS 1.2 support furthermore it is not affected by dozens of security vulnerabilities which your outdated integrated web engine suffers from.