Which among the following is a simple ketone?

Which of the following is an unsymmetrical ketone?

Which of the following aldehydes contains two $-CHO$ groups in a molecule?

What is the compound called if the remaining two valencies of a carbonyl group are satisfied by two alkyl groups?

Write the structures of the following compounds:
$(i)$ $\alpha$-Methoxypropionaldehyde
$(ii)$ $3$-Hydroxybutanal
$(iii)$ $2$-Hydroxycyclopentanecarbaldehyde
$(iv)$ $4$-Oxopentanal
$(v)$ Di-sec-butyl ketone
$(vi)$ $4$-Fluoroacetophenone

Explain the bond formation and structure of the carbonyl group with a suitable diagram.