1) The converts can be converted by holders within 3 months of maturity but Tesla can choose to repay the converts in cash (at the value of the equivalent shares) or a mix of cash and stock.
For the Mar-21 bonds, if the stock price is at $450 in March 2021, convert holders will choose to convert their $1,380m bond into 3.8m shares worth $1,725m. Tesla's call option hedge will be worth $345m & the warrant it sold worth 0.
In this case it is quite likely they issue normal bonds to fund the $1,380m.