There is no need to add money to the account. Unless there is an empty position, even if there is an empty position, the futures company should take the initiative to remind you to supplement or forcibly close the position, otherwise the empty position is the responsibility of the futures company.
3 The opening price is still 100. The opening price has nothing to do with whether it is broken or not. Refers to the price when you buy it, and the loss part is your profit and loss. If you buy after being forced to close your position, the purchase price has nothing to do with the last transaction. The last transaction has been completed and you have been forced to close your position.
You don't understand many concepts. I suggest you read more books, hehe.