Say I have a level 18 bard and want to take the last two levels in paladin. Unfortunately my strength score is only 8, ruling me out. Fortunately a friendly fighter has a belt of hill-giant strength. If I borrow this and attune to this I have a strength score of 21, plenty enough to multiclass to paladin.
My question is this: RAW would the above situation work: can I multiclass to a class I only meet the requirements of due to a magic item?
Bonus points for what happens should I lose attunement.