Whether to use a free https letsencrypt?

1. Yes
2. there are different, LE is the easiest. Pay for a year/two/three. LE for 90 days
3. No

PS
your blog on LE for years-all the rules, part of a utility portal also all the rules

1. There are of course. First, give it 90 days, and secondly, you need to put a bot that will automatically renew.
2. a lot of things that are mainly needed in Eureka - a high level of confidence (more serious checks are issued only Eureka), enumeration of different names, "green dice" with the name of the office. For Eureka, particularly Eureka selling website certificate from a LE - like tights from abibas on the award-winning athlete :)
3. No. Browser absolutely parallel to one publisher