Subdomain

Can a subdomain rank number 1 for any keyword? Like if I make a domain named x1x1x1.org and make different subdomains on it like weightloss.x1x1x1.org, videomarketing.x1x1x1.org will I have any chance to rank number 1 for these keywords?

In theory yes. It is it's own domain like any regular domain. Thing is google doesn't like subdomains so much, so it might be a lot harder to get it ranking well. You're better off just getting a regular domain and promoting that instead of busting your ass to get a subdomain ranking well. It's not the end of the world if your keyword isn't in your domain name....all that really matters is backlinks anyway

You can use a similar strategy by putting the additional keyword in a subdirectory instead of a subdomain.

it is very hard in my experience.

dbpod can make a full sentence?

It doesn't.
It does if you have literally 0 competition and want to rank for "dogs who like candystraws"
It sucks even more than .info, which everyone will tell you sucks a lot to rank.