How start it code ionic again?

Hi community, i worked with Ionic v1 long time ago, but i will want back to develop with this framwork. The problem or my situation is, the angular is not the same, i know the angular 8, is just a number, is a evolution to angular 2, but in my case i don’t code in so much time i want to know the next:

  1. Is necesary pass across to angular 2,3,5,6,7 before start with angular 8?
  2. If don’t development using Ionic v2 and v3, can begin with ionic v4?
  3. What is Stencil or Capacitor?, Should to be a consideration that?
  4. Ionic use angular as the primary languaje, but now support, React, Vue, PWA and Electron. Today they are no longer in React and Vue beta phase?

I will appreciate any help community, thanks.