you can't mix records and if you could you can get there secret base and other stuff but you can't mix records with firered and emerald.
the closest you can be to a gym leader in this game is setting up a secret base with your best Pokemon then mixing records
Mixing records in Pokémon Emerald (and Ruby and Sapphire) is a feature that lets players share game information to influence each other's games and includes things such as seeing their friends being mentioned in TV shows and being able to personally visit their secret base in-game without being connected to their game. After beating the elite four there will even be an NPC representing your friend that has their team for you to battle. This feature is unlocked once you reach Mauville City and its Pokémon center. The process is simple and very similar to trading.
you make a mushroom in alxemy by mixing earth and DNA
CONCOCTION
You pour glasses into others and do the math in your head to get the right amounts. This game is mathematical.
go to a Nintendo event
By Nintendo events or by mixing records with someone that has one
You need to get the Eon Ticket. You can get it by mixing records with ruby or Sapphire that has an Eon ticket.
Mixed RecordsAfter mixing records with a friend, watch television anywhere in Sinnoh, and you might see your friends on TV.
There are two ways to get it: -A promotional e-card called "Eon Ticket" -Mixing records with a person that has an Eon Ticket
Mixing records allows you to get news about whoever you mix records with.
the closest you can be to a gym leader in this game is setting up a secret base with your best Pokemon then mixing records
You could only get it from the Mew event, or by mixing records with someone who already has one. Hope this helps! XD
AFTER YOU GET AN EON TICKET BY MIXING RECORDS WITH POKEMON RUBY, SAPHIRE, OR EMERALD YOU GO TO WHERE THE FERRY IS AND SHOW THE LADY STANDING BY THE BOAT THE EON TICKET AND ASK TO GO TO SOUTHERN ISLAND
YOU COULD RECRUIT IT EASIER BY MIXING RECORDS WITH SOMEONE WHO HAS DONE THE NINTENDO EVENT AND YOU'LL ATOMATICALLY GET THE ARORA TICKET.
no
You get secret island tickets in Emerald by going to special events held in real life by Nintendo.