It seems that I have solved all 3 problems.
1. I used name="banks" and this works fine.
2. I have added a String[] in the ActionForm and used the multibox successfully using the following code:
<html:multibox property="selectedBankIds">
<bean:write name="bank" property="id"/>
</html:multibox>
3. As you told me I used the following code:
<html:submit value="Edit" on*='<%= "return callEdit(" + ((com.fase.ims.logic.admin.Bank)bank).getId() + ")" %>' />
Thanks a lot.