Yes Itachi planned the whole thing, but it didn't come out exactly as he planned. He did actually plan for Sasuke to kill his best friend and fight him with MS. He wanted that because he felt that that was the only way to loose to Sasuke without Sasuke catching on to him loosing on purpose. Get what I mean? He always intended to let Sasuke win but he felt it would be best if he lost to another MS. But when Sasuke fought him without it, he had to improvise and he felt at that point that he couldn't die without Sasuke gaining access to it. I mean if Itachi died and Sasuke's MS didn't activate, there would no longer be a source for him to activate it from right?
I honestly feel that Itachi felt that Sasuke would activate MS himself after some gap in time following their battle. He never intended for Sasuke to learn the truth, but he hoped he'd activate MS eventually, maybe when he started thinking less about revenge (having killed him) and started focusing more on the way things used to be, ie his caring brother. However, as we know, Madara came into the picture, spilled the beans and wall-a instant MS for Sasuke.
The point I'm making is that Itachi always planned on giving Sasuke MS, making him a hero of the leaf by killing him and avenging the Uchiha, and giving him the revenge he always wanted while letting him live. Yes, it was all planned. As for his MS, Itachi clearly gave him all three of his abilities on purpose, but Sasuke could not control them. As we see when Madara shows his sharingan Sasuke, it appeared as Itachi's old one. That means he gave him all his techs and MS but only allowed it to be activated under certain circumstances. Clearly for Sasuke to be able to use the techs freely, he would have to activate his own, unique MS, which he soon did.
As for the techs being very similar, I doubt it was because they are brothers. I think the only reason they were the same was because Itachi physically passed the techs to him and under Sasuke's control, they became slightly altered. The fact that they are slightly different from Itachi's is proof that brothers may in fact spawn different techs. Not to mention all MS's look completely different from each other, even if they are brothers!! The way I see it, all uchiha have at least 10 different techs that can spawn in their MS (prlly closer to 50) and the 3 they can control is completely random. Again it makes sense because Sasuke's versions of the 3 techs differ from Itachi's meaning of those possible 50 techs, if they spawn in more than one individual, it will likely form differently anyway. This all fits into the statement of Madara's that Susanoo is rare.
