Yes , anaemia could be cause for slow cognition. Do a test for ruling out heamoglobinopathies. Language confusion can happen for different languages . Use single spoken language by all , as this is a learning phase of child.

Firstly low hb can cause child to have concentration difficulties and easy fatiguability and lack of intrest in surroubdings. It's  treatable with oral iron supplements Calling him by different names I don't think can cause confusion unless u wake up everyday and call him by a different name. He is too young stop pressuring him and urself