What differences did each one propose in comparison to the previous network? What was the reason for each testnet to be introduced? When was each test network introduced?
The question includes from Testnet 1 to 4 (or even 5) and signet(s).
There are two similar questions 36252 and 9975, but they are old and outdated. I am looking for a detailed historical description and motivation about each test network introduction.
