Doubt regarding the concept

is generic tree necessary for binary tree,because I haven’'t done generic tree,suggest me whether I should start with generic or binary for placement point of view

Yes generic tree is basically an extension of binary tree where you can have more than two children to a node. Placement generally ask much more questions from binary and binary search trees than they do for generic tree as there are no special tips/tricks that can be applied on generic trees like red-black trees or AVL which are features of binary trees, thus creating more potential of questions.
hence focus more on binary trees and its properties.

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