i Register
In some senses, questionless is marked as archaic, rare. Watch for register when choosing this word.
adj
Certain; indubitable; unquestionable; not admitting of question or doubt.
Asking no questions; unquestioning.
adv
Certainly; undoubtedly; without question.
[I]n the firſt of Henry the ſixth, the Company of Armorers in London were incorporated by the name of the fraternite of Saint George: which queſtionleſſe reflected on him, though not as Patron ſpecially of this Realme of England, yet as the tutelarie Saint of militarie men. Elſe to what purpose ſhould the Armorers, whoſe trade is onely deſtinate to the uſe of Souldiers, be made a Corporation by his name, and under his protection.
And do not you perceive a shamefull errour therein? But questionlesse you dissemble it.