A work-from-home request is not leave — say so explicitly. Give the dates, confirm you will be fully available in working hours, and name the meetings you will still attend.
Planned leave usually needs one to four weeks' notice depending on company policy and how long you will be away. Sick and emergency leave is notified as soon as you reasonably can.
For annual leave, generally no. For sick, emergency or statutory leave you may need to state a category — but not private medical detail.
Your line manager, with HR copied. HR records the entitlement; your manager approves the cover.