1. A parallel universe is a different universe that occupies the same timeline. However, the events that transpire in this universe are (usually) independent of all other universes. A different timeline is when something happens in a universe in different ways, at the same time. 2. You can have multiple timelines in 1 universe, but not multiple universes in 1 timeline. That said, there is the (real) theory that every possible action has happened, and that a separate universe is created for each one: While walking, I choose to go left, and another universe is created where I choose to go right. This could be interpreted as both a multiverse and multi-timeline scenario.
1 & 2: These two points contradict each other. If you can have a parallel universe occupy the same timeline as another universe, how then can you not have multiple universes in one timeline? A better way of explaining this might be that You can have multiple universes in one timeline but not multiple timelines in one universe. That said, we either hold in question a point of divergence or a unique point of origin for the universe under discussion. This raises the question, aren't divergences and points of origins manifestations of similar but different universes? This could mean at least 7+ billion (factoring the number of actions taken on the individual, familial, neighborhood, local, city, regional, state, national, world level and so on) iterations of our universe as we may imagine it from our scope of scientific knowledge on on this planet.