Its generally depends on many factors, which determines the amount of loan approval.your credit profice and other factors contributes to your loan approval.

It depends on your credit profile and lenders.

keep in mind that when your shop for auto loan or more credit, lenders places and inquiry on your credit score, so if you are doing this often your credit score will add up which can have negative impact for your loan application. so if you can avoid too many enquiries just do that.

Yes you can avail discount plans just provide the lenders with details and avail the offer.

yes cosigners can be helpful in those situations where you are not able to provide all credit requirements.

Repayment and interest rates depends on your credit profile. And also different lenders have different repayement terms and conditions and interest rates. you just need to know all about these things before application to the lender.