Tax Break for Interest on Personal Loan Used for Stock Purchase

Hello Turbo Tax Experts, 

 

I read online that there are tax breaks for personal loans used to purchase stocks but they are very limited in scope. Please help me better understand what the scope is. 

1) Is the tax break restricted to just stocks or do ETFs count for the tax break too? 

2) Are there specific types of stocks if purchased using the loan, that are excluded from the tax break? 
3) So if a person takes out a person loan at interest rate 7% to buy stock, would the tax break be whatever they pay of that 7%?