Nope, in tobi vs minato chapter you can see tobi uses a 3 tomoe sharingan to control the kyubi. Im guessing he used the same on yagura
Yes you can gain it one eye but because the other eye with a MS will cause strain, drain chakra and eventually go blind, the person will most likely try implant it in both eyes. The ems in the one eye wont cause any strain though.
(First quote) Its still confusing about the fact that itachi stating that you can contorl bijuu with ms or higher, yet we see tobi controling with just plain sharingan. This could sugesst only one thing...tobi is the uchiha clan ancestor. Reason beng, tobi containing the uhcia ancestors "eyes" since the uchiha clan ancestor was the only one with formiddable chakra and great spiritual energy before madara obviously. Plus, even madara wasnt able to control the kyubi with just his sharingan, he had to push it to the next stage; ms form.
(Second quote) This partly contadicts what i said. Ems can be wakend in one eye but will not cause strain or blindess. Which leaves me wiht one question(well actualy two questions in one sentance

). Why didn't madara only take one eye from his brother and also why didn't kakashi ever get a chacne to awaken a ems? Kakashi would be even more poweful surpassing itachi and izuna wouldve still been alive.