Your payments go towards both interest and principal in a proportion that varies over the lifetime of the loan, such that your time frame is set by the terms of the loan. If you get a 30-year fixed rate mortgage, you pay it back in 30 years, regardless of the loan amount or interest rate. Look up "amortization table" if you're curious.
You mean the repayment amount? I'm not sure what you're asking.
Of the lump sum price (principal), interest rate, loan term (time), and monthly payment, you can only change three of the four, for a fixed rate loan. The fourth is defined by the combination of the others.
Yes of course it has. You've just over doubled (interest rates are low but they're not nil) the time it's taken to pay back that loan.