1-2 days, they will call u to verify application within a few hours if on working day, then usually the same day or latest following day will get notification.

through email

yes, its possible and i have done that with MBB.
To answer your question, it is ii) 15k x 80% = 12k.
bearbear it make sense to pro long the payment period with same amount of money, consider below scenario.

assuming zero outstanding, no new transaction, and allow 100% of available CL to be used for BT for ease of explanation.

MBB CC CL is 5k, and deposit 7k cash into it, so the available CL is now 12k (with 7k credit in the account).
If we BT 12k from other bank to MBB for 12 mths plan, effectively the monthly repayment is 1k, since we have 7k in credit, we do not need to pay single sen for 7 months.

Whereby had we BT 5k to MBB and paid the 7k cash to other CC, we will have to pay  RM416.67 (5000 / 12) every month to MBB CC.

indirectly consider locked, because in above scenario, the available credit limit for spending is zero.