RE: I have doubts about HIVE, maybe an expert can help me

I am not an 'expert' on Hive per se, but I can provide some personal info from experience.

1: I am not sure if you can upvote your own posts/comments, I've never tried, but I would say it is generally frowned upon if you did.

2: There are many searchable posts that describe the 20% APR from HBD savings. Here is one for you to peruse: https://peakd.com/hive-167922/@rentmoney/hbd-savings-and-apr

There are other results with more in-depth explanations to be found if you type in 'Hive Blockchain 20% APR savings' or something similar.

3: I am not sure on this one. Personal Research is critical while looking aspects to a feature on a Blockchain,

I hope this helped somewhat! Good luck on Hive and be sure to explore the ecosystem to find a dApp or service that best suits your needs.