I've been researching water grains on this sub and the internet but a few things are still unclear to me...

1. I've read that after the first batch, the grains may not be completely "active". Therefore, is it a good idea to keep your grains in water for longer than 48 hours during the first batch? Or, if I should transfer them to new water and sugar after 48 hours, is that because the grains need fresh "food"/sugar?
2. Why does the second batch need to be in an airtight container?
3. I want the grains to consume as much sugar as possible during the 2nd batch (I don't want any sweetness). Does this mean I need to ferment longer than 48 hours? And does anything else special need to take place to get the grains to consume all the sugar?
4. During the first batch, can I cover the jar using a paper towel and rubber band? Or is a paper towel not a good idea?
5. As far as mineral content goes, is brown sugar alone good enough? Or will I need to add some other minerals?
6. Lastly, I'm prioritizing maximum number bacterial strains over everything else (taste, color, sediment, fizziness). What aspects are most important when it comes to getting maximum bacterial strains? Length of fermentation? Changing batches often?