#1 Looks like they didn't approved your comment. Commenting on other's blog is a good way to create backlinks. But if they mark your comment as spam, then it will be a trouble for your website and post.
So, you have to make a comment which is related to the article and use the link as hyperlink. For example, check a comment from that post.
#2 It's fine. But according to SEO terms, it would be better to use the link from hive.blog as this link already have the keyword(Hive) in URL.
But I am surprised to see that PeakD's Domain authority(38) is higher than Hiveblog(36).
So, It's upto you actually.
#3 I already talked about it. This article may help you.
Let me know if you have any other question. Feel free to knock me at discord - Marwan#4591