If you're asked. Some employers ask for a CV, others want an application form. Some will take either. Never send a CV if an employer specifically requests an application form. One or two but never three' is our basic rule.
Most students opt for two, which seems widely acceptable.
A well thought out one pager looks great but can be hard to do. In general include all work experience, paid or unpaid, however unrelated. Expand a little. You don't have to have a section headed 'Responsibilities'. Explain your involvement.