Block Cipher Modes of Operation

In this video, we will discuss the different modes of operation of a block cipher. A block cipher processes the data blocks of fixed size. Usually, the size of a message is larger than the block size. Hence, the long message is divided into a series of sequential message blocks, and the cipher operates on these blocks one at a time.
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Q1. In which modes of operation do we need Initialization Vector ?
Q2. In which modes there is no feedback from previous stages?