Joining INTO many-to-many table (From Primary Key Table)
http://sqlfiddle.com/#!9/33b19d/3 ...

as I said in the comments - use left join instead of inner join ... 

your diagram misses the mentor_types ... so I commented it out.

of course you will get 2 lines for user 1886

For your question regarding all lines of user_mentors - no its impossible if you start building the select with the users table. And as there is no mentoruser_id that points to other lines than the id==4 line in users_mentors.