“8 WEEKS DIFFERENCE!!! Eeeek. No longer using my essential brown hair spray to cover those gaps. I haven’t bought or changed to any special hair products, just your own dermaroller and oil, which I love!”

No. You are in full control of the pressure, so it stays gentle. A little tingling around the edges is normal and just means the scalp is being stimulated.
For the first month, dermaroll and oil every 4–5 days. After that, reduce to once a week. Use the shampoo and conditioner as normal on wash days.
Sulfate-free shampoo lathers best on oil-free hair, so rinse thoroughly with water first, then double shampoo to make sure the oil is fully removed.
The hair growth oil, shampoo and conditioner are suitable. The dermaroller is not suitable for use on any inflamed, irritated, broken or damaged skin, including skin conditions such as psoriasis or eczema.
For the best results, yes. Each product plays a specific role in the system, and together they work far better than any one of them alone.