For the first question, the correct answer is:
It would divide the Confederacy in two.
Controlling the Mississippi River was a strategic goal for the Union because it would split the Confederacy and disrupt their supply lines, making it harder for them to move troops and resources.
For the second question, the correct answer is:
They hoped to have greater freedoms under a Confederate government.
Many Native Americans aligned with the Confederacy because they believed it would grant them more autonomy and rights compared to the Union, as well as a desire to protect their lands from encroachment.