is statement of account required for a student visa to china from Kenya and how much is needed?

According to the policy, there is no such a requirement on the bank statement, but if you can provide, it may help a lot for obtain one in the end.

policy z it applicable to Kenya alone?

Hi, I am not very clear about the "policy z" mean? Do you mean the Z working type or any other information?

I mean is the policy applicable to Kenya alone or all other African countries?

The Chinese visa policy is applicable to all the African countries that have diplomatic relationship with China. But they are a little bit different for different countries. For instance, some countries such as Kenya people do not need to show the bank statement, but other countries' need to.

You need to local Chinese embassy for consulting more specific requirements.