What is the maximum throughput (tx/s) that some systems can achieve?

Do you really need to go through all the history of the system in order to be convinced of the latest state?

What are the different ways to decide who should be the next person that gets to choose the next block of transactions?

Can you hide the amount you’re sending? What about the recipient? Or your own identity?

Can you transfer bitcoin into ethereum or more generally one cryptocurrency into another?

Is it possible to send funds to a recognizable shortname instead of an hexadecimal string?

Are there ways to protect your funds with several keys instead of a single one?