It will give one main band at ~66 kDa. You will probably also see bands for aggregates at multiples of 66 kDa. Impurities may also show up at various masses if it is not highly purified.

In general, one band should be observed at around 65 KDa for pure BSA. However, to make sure of the specificity of this band to BSA, you can transfer to nitrocellulose membrane, and expose to BSA antibody.

Depends on the purity. As it's precipitated from serum, there might be some contaminants, e.g. IgG.

There would be a specific band at the protein weight of BSA i.e. ~66KDa and some non-specific bands depending upon the purity of the product.

You will get single specific band at around 66 KDa. other non specific band may be present , depends on the purity of the BSA sample.