I'm not too familiar with some aspects of Scottish law, but I believe as far as trials go, their system is much the same as in England and Wales. If so:
(1) Only if the defence agrees to it. If they do your evidence will be "read" to the court. If they do not they have the right to have you attend court so that they can cross-examine you. If you fail to attend your evidence cannot be admitted.
(2) You cannot withdraw a statement. Once it's made, it's made; you cannot "unmake" it. You may make a retraction statement contradicting the facts you provided in your original statement. If you do you may still be called to give evidence and when in court you may be declared a "hostile witness" which means you can be cross-examined by the prosecution to explain the differences between your two statements.