I have an android application, In which home page comprises of 8 ImageViews, they act as menu options for users, So where should I put the multi-density images for these ImageViews in custom drawable folders(ldpi,mdpi,hdpi,xhdpi,xxhdpi,xxxhpi) or drawableV21 or drawableV24 ?
It changes due to your need. For images, you can design them for the highest resolution and put them in xxxhdpi folder. Android will automatically downscale resolution for other devices. Also, you can put different drawables for different resolutions. But they should have the same name.
For drawableV21, drawable24 depends on the version you want to run your app. if you put a drawable v24 and not put anything with the same name in the drawableV21 folder. Your app will crash below Android API24.
So you should use this folder to show different drawable or other assets for different API Versions and resolutions.