Do you have any Local transaction in your wallet? If so, remove it and try making the tx again.
I do not have a local transaction but I have an unconfirmed transaction. Is this related to this transaction? If yes then how?
Thanks in advance.
Im not sure. Since you received the missing inputs error, you must be trying to spend the inputs coming from the unconfirmed transaction. Would you mind sharing the tx id of the unconfirmed tx and try making your tx again, but this time pressing Preview, Copy and pasting what you get here?
Is this instruction necessary for installing every new update?
No. Usually, you can just download and install/run the new update. No need to uninstall the old version.