It maybe depends where the birch plywood is from? I know the Germans use it for most of their houses and wheels but they say it's made with non toxic glue.
Huri - The house I used was one I bought, but it is basically - a box - with some holes cut in for doors. Cutting holes would be a bit too much diy for me. The dowels for legs are easily bought in hardware stores and are cheap. I actually used non toxic wood glue to stick those on as it's stronger. If you can find a pet-safe, non toxic wood glue, then the legs would be stronger. I made sure there was no glue residue visible - that way the glue can't be chewed. Once it's dry it's not toxic anyway, but best if none showing.
Someone on here used this as a house (adapted I think). If turned upside down it could make a platform/shelf - although I'd be tempted to cut one of the sides out so it's open underneath. And check the size of the gaps. Is it for a Syrian or dwarf hamster.
KNAGGLIG Box Pine 23x31x15 cm - IKEA