Do I need to come down to your retail shopfront to buy with installment?

Not necessary for Grab Pay Later installment. You can purchase online. However if you want to make split payment with installment, you have to come down to our shop. For DBS/POSB credit card installment also, you have to come down to our shop at #02-65A Peninsula Plaza since we do not have online payment gateway for it.

Do I need to have balance in my bank account to get installment credit approval?

Yes for Grab Pay Later installment with debit card because Grab will deduct first payment from your bank account immediately upon purchase. If you do not have sufficient balance, the first payment will not be successful. For credit card, it may not be necessary to have sufficient balance but your credit limit must cover total purchase amount.