How do search engines treat domains and subdomains?

Question

Search Engine Optimization

Good day.
Interested in how search engines treat sites that have several domains / subdomains and the content on them can be duplicated.
For example:
1. An online store with subdomains for different cities, the product catalog is the same for all. How will search engines index such a site, will there be sanctions for duplicating content?
2. A site has been created, the domain of which contains 2 words separated by a hyphen. Both domains were purchased: slovo1-slovo2.ru and slovo2-slovo1.ru, in order to avoid registration with competitors. What is the best thing to do in this situation - send both domains to the site, and index both, or make a redirect on one?
And another question for those who know. How Yandex and Google relate to thematic domain zones - such as .media, .photo, etc. Do they take into account the meaning of words in the first level of the domain, and will such a site be a priority for issuance?
I would be grateful for criticism and any material on the topic. Totally new to SEO

Answer 1

For this, both google and Yandex have tools for webmasters. Where you can specify mirrors and control indexing.
In addition, in theory, the canonical url can help, which will be indicated everywhere, and lead naturally to the main domain:
https://support.google.com/webmasters/answer/13906...

Answer 2

domain and subdomain are different sites for search engines, but it is better to tie everything to one site and the massiveness will be higher