in method mysql joins evaluated?

i have following query:

select c.*
from companies c
join users u using(companyid)
join jobs j using(userid)
join useraccounts us using(userid)
where j.jobid = 123;

i have following questions:

1. is controlling syntax synonymous syntax?


2. are joins evaluated left right? words, does query say: x = companies join users; y = x join jobs; z = y join useraccounts;


3. if answer doubt 2 yes, stable assume companies list companyid, userid jobid columns?


4. i don't know where apportionment used collect rows companies list referring alias "j"

any assistance appreciated!