a. First button from the right is the Reset button
b. The second or middle button is the Feed button
c. The third button is the Record button

It can be disassembled by taking out the top by pressing it from the back end and both left and right sides.

Yes there is a voice recording feature available and it can be set manually.

It need 5v to work.

Yes buttons can be affected if the towel would be too wet because in this case water can go in and affect its function.