If one of you is using the old mp protocol, and the other is using the 2017.2+ mp protocol, then you'll see weird things like you've mentioned. This can be set in the mp connect dialogue in-sim.
I have tried both mp protocol versions on May 30th 2018 and according to Jomo it's still "weird" (Landing gear not right and wrong livery).
I would say its because of different FG versions but this issue happened when I had the same version as Jomo, so that's not it either.
Sorry guys, but I have to say you are wrong regarding MP version. This may show on the film of May 30th 2018 when I selected MP version 2 Jomo didn't even see me,
when I selected MP version 1 Jomo saw me but landing gear not right and wrong livery.
HELP
AAL4955