1. His mystery series are always popular.

2. His mystery soap operas are always popular.
---------------------------------------
Does #1 mean #2?

2 answers

1. His mystery series are always popular.
2. His mystery soap operas are always popular.
---------------------------------------
Does #1 mean #2?

3. When I start writing a new series, I usually stay up late for days.
4. When I start writing a new soap opera, I usually stay up late for days.
[Does 'series' mean 'soap opera?]
A series can consist of topics including soap operas and other themes. There are police-drama series, law series, doctor series, and others. So no, "soap operas" and "series" are not interchangeable.

https://www.imdb.com/title/tt0106079/?ref_=nv_sr_1 and https://www.imdb.com/title/tt5290382/?ref_=nv_sr_1

https://www.imdb.com/title/tt1442462/?ref_=nv_sr_1

https://www.imdb.com/title/tt0413573/?ref_=nv_sr_1