Answer 1

you should be fine, sql is not very hard to understand and you can pick the basics up on the fly. but if you are worried you could of course do the sql course here on sololearn.

Answer 2

Kaimi i don‘t think so, learning is not always linear. if i were in your position i would just start and pick everything up that i need on the way. of course you could learn about cgi and webservers and nosql before you start but i think it would be best to just start and learn whatever you need on the fly

Answer 3

Kaimi, You can learning both in parallel: Ruby lang & Rails framework + Git + Linux terminal.