How do synonymous variations of the same semantic expressions and SEO text spamming affect page ranking?

Question

Search Engine Optimization

Does it make sense to use all sorts of synonymous variations in the seo text?
1) For example, instead of "installation of cable systems" use many variations in different parts of the text: "installation of cable systems; laying of cable systems; installation of cable systems"?
2) Another example: together with the phrase "buy server hardware" use "order server hardware" and "price of server hardware" is it worth it?
3) The text.ru service shows the characteristics of spamming - does it take these synonyms into account? What percentage of spamming on text.ru / on other services should be followed?

Answer 1

1) Yes it is. In addition, see digrams and LSI words.
2) worth it, but dilute it - otherwise there will be Baden-Baden and overspam.
3) Write in support text ru