You'll need a proprietary glue removal product for glue spots if you have any. Goof off is the product most mentioned here, though it does depend on your location as to how easy it is to get hold of. Soft wire brush (brass bristles) helps work it in to the wood.

If you want to try and 'pop' the flame, then yes, a dark stain, rub back, and then your main colour stain. Here, you'll need to be rougher and maybe use something like P240, but gently. Ideally you'd want to use a finer grit, but as I've said before, experience has shown that anything much finer than P240 tends to polish the surface and make stain uptake patchy.

But you've only got 0.5mm-0.6mm of veneer depth to play with, and if you take too much off you'll start to see the wood beneath, so be very gentle with the sanding.

The back and sides are a basswood laminate, but with a figured basswood veneer on the outside. So whilst you wont want to pop those, you still need to be careful with the surface, so always best to be as gentle with it as you can. It's smooth enough for finishing, so a once-over with P800 (or higher) just to remove loose surface fibres, but you could even wait to do that until after staining.