My target is an full Ironman finish. Should I do the training for a Sprint then an Olympic,and then an Half, before the full or can I just go right away to full Ironman plans?
Of course I can do the minimum workouts specified at Ironman-0 training plans.
You do not need to go through the progression of Sprint, Oly, and 70.3 before you complete an IM. Certainly, it makes the experience a bit less “steep” but with the right IM plan, you can have your first triathlon be an IM (my second triathlon was an IM after an Oly).
The 80/20 Level 0 plan is designed for a first-time triathlete, and I can confidently approve you using it for your first triathlon. In fact, many Level 0 athletes end up switching to Level 1 ~8 weeks into the plan as they become more and more comfortable and fit.
However, don’t disregard the fun it can be to create a journey that does take you from Sprint to Oly to 70.3 to IM. It’s not necessary, any more than it is not necessary to hike through Europe when you can fly. One gets you there quickly, the other might be a more rewarding experience.