Bots are a bit of a ongoing debate on here. They get used alot but some people think it sacrfices quality (as you can just buy votes).

Not sure about free bots dont think so...

As far as i know bots are legal as there arent really rules on here as such.

For good guides about steemit i recommend following @ilyastarar. Im sure hes written in depth about bots in the past

Hope this is helpful for you 😊😊