I’m no expert but I worked for a sports turf maintenance company.
We dealt with anything grass related.
I was never involved with chemicals but know a lot of the old methods were banned under EU regs.
Each green keeper has their own methods depending on the type of soil.
So no answer fits all...
Think it was started years ago .
Teams employed a lip reader to hear what subs and coaches were planning ,coming on so they knew their tactical changes.
But seems the norm now.
Yes medal/stableford sets your handicap
You can’t have several 8/9 on holes in that format.
But you could win holes in matchplay with a 9 as long as your op has a 10.
That’s because most UK players prefer social golf for a pint or coffee.
They don’t want to have a card in their hand every time they stand on the first tee.