Can memories of basic skills ONLY be unlocked through Memory Charm upgrades, or will a character be able to re-learn it through outside assistance?

For the example of forgetting how to tie shoelaces, would it be a matter of having (a) a third party show them how to do it, and then they could remember that, (b) they would only remember that someone tied their shoes or helped them but not retain the skill, or (c) they would not even know what it means to tie their shoes even when shown?