ofcourse user B put to supply btc more than 1000$ ... @officialjustlend

Answer2: If User B liquidates, it means that the amount of money lent out is greater than the amount of money supplied, resulting in a shortfall. This means that the collateral factor and reserve factor are not sufficient to cover the amount of money lent out, and the system will trigger a liquidation. This liquidation will affect all users that have supplied money, as they will not be able to withdraw their money until the shortfall is covered. This means that User A will not be able to withdraw his money until the shortfall is covered. In addition, the APY will be recalculated continuously as the supply is too low, resulting in higher APYs for the suppliers.

nothing happens to User A if he did not borrow, he get paid Rewards, also u need to check Collateral factor, and reserve factor which triggers Liquidation