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Yeah, that drops through Twitch system is a big brain idea I think. Awesome deal for both parties.
And yay, thanks!
As far as I can understand Hive is a clone (fork) of Steem. Lots of people and dApps have already switched to Hive, right? I can see that I got my account and wallet cloned too. From now what I post here won't appear on the other blockchain. Should I be using Hive only? If not, should I just copy-paste my posts to both sites? Or should I entirely get rid of Steem? Does SBI work the same way for Hive? Is there any minnow booster program going on Hive? Should I use eSteem or hive.blog for posting?
I have infinite questions. Also, I am curious about trends and which apps are 'hot' right now.

Yes, Hive forked from Steem. Simple version of why: Conflict between witnesses and Justin Sun caused the witnesses and most (I think, actually do not know) of community to move to Hive. There is a tldr here: https://hackernoon.com/inside-trons-steem-takeover-attempt-and-the-birth-of-the-hive-blockchain-ya1g63249 whole thing is however written by a pro-Hive, so the accuracy of the events might be slightly in Hives favour!

Posting on Hive does indeed not show up on Steem. Some apps support posting to both, I think Actifit being an example of one.

You can copy-paste to Steem (or vice versa or only use Steem), what you want to do depends on how you feel about Hive and Steem. If it matters to you, do a little research (search for hive, steem, tron, justin, fork, attack, exchanges participating etc) and decide what you want to do from there. I only use Hive, but left my Steem account as is and put it to follow Curie curations, there are regular users on Steem posting content that can enjoy a vote or two. Not sure you can say Hive fixed the problems that were central to the conflict on Steem. If it was centralised to Steemit on Steem, it is centralised to a few top players on Hive. But there is at the moment a much better chain-health in that there are API servers operated by more people, compared to Steem which bascially only had 3-4, two of which was Steemit (now only 1 I think and it is Steemits).

HBI works the same as SBI.

Can't recall but minnow booster had a variety of programs? If you mean leasing, then for example https://hive.dlease.io/ I believe is an option.

You should use https://peakd.com to blog of course! Nah, you can use whatever you like that supports Hive. I find peakd to be the most complete app to do all sorts of integration with Hive, voting on witnesses, proposals, checking stats etc.

Trends and hot apps not sure about. A while back I found https://3speak.online/, a video site similar to d.tube but at least for me it seems to work a lot more reliable. They have also done a good job of sort of hiding away the blockchain bits, making it more a site about "hey join and post videos".

Holy molly, that was one thorough answer! Thank you very-very much for all the info, I have a better understanding of the situation now.
I'll need to do a lot of reading and research :)
If I can help you with anything please let me know.