Can shares be counterfeited

Answer 1

Assuming you mean shares of stock, the short answer is "no". While stocks and bonds used to be issued in paper form, modern trading is electronic with many checks and balances. Clearing houses and brokerage firms know exactly how many shares trade at what price and to whom they were sold. You could theoretically fake a stock certificate, but in modern trading no one would take that at face value without verifiable proof that you actually own the asset (i.e., a balance in a brokerage account that can be verified).