It depends what you mean also by downgrade a library? However the added features in Kontakt 5 means patches made or resaved with Kontakt 5 will not open in Kontakt 4. Kontakt shows Backwards compatibility in that patches or NKI from say Kontakt 4 will open in Kontakt 5. Kontakt & Forward compatibility & all that Is not a dumb question Short answer, NO it's not possible.
