What is involved in adding a second liberal activity to my microenterprise?

I currently have a microenterprise which focuses on online tutoring, but next month I will receive my diploma in clinical hypnotherapy, and I’d like to add my hypnotherapy practice to my microenterprise. Currently, I’ve opted for the Versement forfaitaire libératoire. I have a few questions regarding how adding this second activity will affect my microenterprise.

1. What is involved in adding a second activity? Will this change the percentage that I will pay in cotisations, taxes, or CFP in any way, or will things just stay the same (meaning that I pay the same percentage of charges on a higher level of revenue)?

2. My understanding is that I can stay in the microentrepreneur scheme as long as my revenues for these liberal activities do not surpass E83,600, but that if my gross revenue exceeds E10,000 for two years in a row, then I will have to open a second, professional bank account instead of using my personal one. Have I understood this correctly?

3. I read that, in order to continue opting for the versement forfaitaire libératoire, my reference tax income for year N2 of my microenterprise has to be less than E29,579 (I am a single person). Does this mean that if my revenues exceed this figure, then I can no longer opt for this, and what happens then, if this is the case?

4. Regarding the references to year one, year two, etc. of the microenterprise, are these dated from the start of the microenterprise (August 2024), or from the first full financial year of operation (2025)?

Thank you for your help, and apologies if I’ve asked any questions which seem obvious - I’ve researched these questions as much as possible myself before resorting to asking these questions here.