The free version of Instrumentation Tutor is a great way to try the app for free. Access to some content is locked, but there should be enough to help you make an informed decision about whether or not to purchase the full version.
The app's 'Instruments' section contains detailed instrumentation for orchestral instruments. Range, transposition, registers, timbre, clefs, tuning and foreign names are all included.
The 'Reference' section displays general knowledge and topic explanations.
The 'Quiz' section provides a customised learning experience where you select the instruments, ensembles and topics you need to memorise.
The full list of included instruments is below.
Woodwind: Flute, Oboe, B♭ Clarinet, Bassoon.
Brass: Horn, B♭ Trumpet, Tenor Trombone, Tuba.
Pitched Percussion: Timpani, Glockenspiel.
Unpitched Percussion: Snare Drum, Bass Drum, Crash Cymbals, Suspended Cymbals.
Bowed Strings: Violin, Viola, Cello, Contrabass.