For example, the first value should be "yandex.ru" or "yandex.com", not just "yandex" (because this is not actually a URL).
1. Why is Google Analytics showing non-URL values in this columns?
2. And is there any way to get the actual full referrer URL?
you should create a custom report and add to them:
page(to see where traffic comes in)
source(which provides only a domain of referrer)
referral path(which is the full referrer url, but without domain)
- if interesting, add as a metric
After you build it up, export it and merge columns with source and referral path to get full referrer urls.