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Both (but it was mainly meant to be factious, sorry).
https://www.youtube.com/watch?v=z_a0e7XpSqk
As said, you can't really lighten dark leather. To the extent you can, you run a high risk of it looking shit.
Depending on how visible the tongue is, wash it with moisturising hand soap, then go at it hard with acetone and see if it lightens. If it does have a crack all over.
Your best bet is to sell them and buy some that are a more suitable for the project.
I don't know if it is sarcasm or a real advice on a video that could interest me, but I will reply as if it was the latter.
I did not want to make my shoes"look expensive" or whatever, it is nothing price or value-related.
I just like shoes with light shades and subtle color tones, and I find that their current color which is plain dark brown could be really nice with subtle lighter brown reflections