>>2
> why should I trust free proxies

You probably shouldn't. It's just a technique to be used in certain situations.

I have experienced anecdotal evidence that tor doesn't provide anonymity when doing this.

$ torsocks youtube-dl link/list

while I have annectdotal evidence that

$ proxychains youtube-dl link/list

Goes un noticed when I chain 3 additional proxies from different countries.

I'm not going to explain what that evidence is.