The only way that would work is to strip off every bit of the finish that covers them first. That's a LOT of work. A LOT of work. And then, MAYBE wood bleach would lighten the stain. Maybe not if it's an aniline dye. The only true way to make dark wood cabinets be a ligheter wood would be to sand out all of the old stain that's penetrated the wood. That's VERY risky, as some of the stain may have penetrated further in some areas than others.

You can always paint them. Or if you chemically strip off the old finish, you could attempt to do them in a cerused finish since they are already dark. But that doesn't traditionally work with birch. It needs an open grained wood like oak to be the most effective treatment.

If the cabinets are older, examine their construction and wear carefully before committing to such a time intensive project. Many times on older cabinets, it's not worth the effort and replacing them entirely at some future point is a better plan.

Not in this lifetime.
If you add your time, $$ and iffiness to it, you're better off to buy new doors.

It's very time consuming, requires meticulous sanding and application of nasty chemicals, and seldom works very well.

I'd paint them.

Bleach is a corrosive material. It might permanently damage the wood, even if evidence is not visible right away.