Rapid cycling is if you experience 4-5 (or more) cycles per year.
Mixed episode is if you experience (hypo)mania and depression at the same time for a week or more.
A depressive episode lasts for minimum 2 weeks.
A (hypo)manic episode lasts for minimum 1 week.
Baseline is when you're neither.

Rapid cycling is a form of BP. But BPers do NOT cycle several times per day or per week, an episode usually lasts 2-3 months.
There are DIAGNOSTIC CRITERIAS for the episodes, specific in regards to time and symptoms.
Being sad one day and happy the next is not an episode.