1 Excess will be deducted from any payout.
2 It's your property until you ACCEPT any offer, so just stipulate that you retain title(car ownership), they are duty bound to settle, and in practice unless car severly badly/dangerously done won't have a problem, buy back cost normally 10% - 20% of market value.
3 Has to be Mot and roadworthy, but you may find some that aren't bothered as they get crushed anyway!
tabetha