Confused by engineering

In order to prepare for a longer trip outside the bubble, I wanted to upgrade my FSD to G5 (I realize there's a pre-engineered FSD one which is better, but I don't want to spend that much time to collect materials).

I have Grade 5 access with Felicity, since I handed in a lot of cartographics. I already noticed that I have to create a modification for G1 before I can one for G2. I'm now at G3. But this time, one modification didn't allow me to move to G4.

Does this mean, I have to create multiple G3 modifications now before G4 is available?

The UI is pretty confusing, but to me it looks like you get all the bad things immediately (like "power draw"), but the good thing (in this case "optimized mass") starts imperfect but gets better when generating the modification again? I assume that "optimized mass" is at 60% now (based on the circle and the blue dashed line).

So I assume that this percentage increases the next time I try this G3 modification? And as soon as the ring is completed, G4 is unlocked and the game starts again with G5?

But what does this mean for the current G3 version on my FSD? Is it basically sub-optimal and I should re-generate the modification until the "optimized mass" circle is full?

In summary, my questions are:

• do I have to generate more G3 modifications until G4 modifications are available?
• how many G3 modifications are required in total?
• are the 1st modifications on a specific tier "incomplete" and therefore my current 5A FSD (G3) is not the optimum?
• should I re-generate the modification on the same FSD or use a new one?
• are there other ways to unlock a tier, besides re-generating modifications?

Thanks! 🙂