Is there any way to add pedals & training wheels to this balance bike?
You could probably add training wheels, but not a crank. There simply isn't anywhere on the frame for cranks to go. Also, adding training wheels to a balance bike is kind of defeating the purpose of a balance bike. It's meant to be an alternative to training wheels that allows the child to learn to steer into falls and "scoot" around and eventually learn to glide around before riding a bike with cranks on it. These have been pretty universally hailed as the best way to teach a younger child to ride. Oh, and with the shape of the frame, you may not be able to find an appropriate set of training wheels too, they would end up at a forward angle, and would be more likely to get in the way of the "scooting" action kids do on these bikes.
No, not possible.
If you want to go the other way, buy a 12 inch bike and then remove the chain/pedals/bottom bracket/bearings and degrease it. Store the parts so they don't rust. Optionally put something over the ends of the BB tube to protect the threads, even some duct tape would help.
When the kid is old enough, refit all the transmission parts.
The plus side, the kid has one bike and may transition to pedals easier because its still the same bike.
Downsides, the rear wheel will have a sprocket unused, and the resulting bike will be heavier than the balance bike pictured above.
Do consider not using training wheels - a Balance Bike removes that need completely. Once the young rider can ride ~10 metres without touching the ground with their feet, they don't need training wheels.