The correct option among the given choices, which is not correct about the Cabinet Mission Plan, is Option 3: Acceptance of Pakistan.

The Cabinet Mission Plan was a proposal put forth by the British Government in 1946 to resolve the constitutional deadlock between the Indian National Congress and the Muslim League and to pave the way for India`s independence. Let`s examine each option in detail:

Option 1: Provincial grouping

The Cabinet Mission Plan did propose provincial grouping as a means to address the concerns of various religious and ethnic communities in British India. The plan suggested the formation of three groups of provinces, with each group having its own executive and legislative council. This option is correct and aligns with the provisions of the Cabinet Mission Plan.

Option 2: Interim Cabinet of Indians

The Cabinet Mission Plan did propose the establishment of an Interim Cabinet of Indians. It aimed to create an interim government composed of Indian leaders from both the Indian National Congress and the Muslim League. This interim government would work towards framing a new constitution for India. Hence, this option is correct and in line with the provisions of the Cabinet Mission Plan.

Option 3: Acceptance of Pakistan

This option is not correct about the Cabinet Mission Plan. The Cabinet Mission Plan did not specifically propose or accept the concept of Pakistan. Instead, it proposed a decentralized federation where power would be shared between the center and the provinces. The plan aimed to provide safeguards for the rights and interests of different communities, including Muslims, without explicitly endorsing the creation of a separate state based on religion. The demand for Pakistan emerged later during negotiations and discussions following the Cabinet Mission Plan. Therefore, this option is incorrect.

Option 4: Constitution framing right

The Cabinet Mission Plan did propose that the future constitution of India should be framed by an elected Constituent Assembly. The plan suggested that the Constituent Assembly would consist of representatives from all the provinces and be responsible for drafting a constitution for a united and independent India. This option is correct, as it aligns with the provisions of the Cabinet Mission Plan.

In conclusion, the incorrect option about the Cabinet Mission Plan is Option 3: Acceptance of Pakistan. The plan did not explicitly accept or propose the concept of Pakistan but focused on a decentralized federation and the formation of an interim government to frame a new constitution for a united India.