Not world records, not sure about national level.
no
yes
A: No
Go To Any Pokemon Center In The Game And Go Upstairs And Go To The Union Room And Enter And Talk To The Person You Want To Mix Records And It Will Say "MIX RECORDS"
yes
No they can set at any official meet
There Are 493 Pokemon Through Out The Whole World Of Pokemon :]
Pokemon indigo i think
You can only mix records between Pokemon ruby, sapphire and emerald not leafgreen.
Guinness World Records do not pay any money to those who break or set records. However, they do award an official certificate of the achievement free of charge.
Two people on separate DS's must go to the Link Room upstairs in any Pokemon centre (middle one). Then one talks to the other and chooses Mix Records (or sumin close). The other one accepts and then they both press A to mix records.