var_qstn_ivuinstr
Usual activities means the work or duties that are performed regularly, including housework and agricultural work. For children, this also include attending school. So if a child was unable to go to school for 2 days due to the illness, you should write 2.
Question post text
If none write zero.
If answer is 0 > Go to 12 (h12 - variable name in dataset).