Kakashi can't copy it.If he were able to he would have done it.
CONCLUSION
1.FTG is a gekkai genkai.
2.His eyes can't understand the jutsu combination.
What is FTG?
please tell.
Flying thunder god technique
you can't copy ninja tools, FTG has specific ninja tools to it, its not just instant teleportation
the kunai that used by minato has jutsu combination on to it. A ninja with sharingan normally able to understand jutsu combination.
so how come tobimara and minato are linked?