1
while using an offline client I have to copy and paste transaction history of the address I want to spend coins from. What if there was a new bitcoin transfer into my address before sending the signed transaction to the network? Does the transaction fail? or work fine because there are more bitcoins than shown in transaction history
3
It will work fine.
The offline transaction you are signing points back to one or more previous transactions that sent coins to your address; these are the coins that the new transaction will spend. It's okay if additional transactions come in in the meantime, they just won't be the coins used as the inputs for your offline transactions.
