I called to terminate my UOB Plat ONE after years of using it, because I do not use this card much, and do not want to pay annual fees. After few days, they call me to offer auto annual fee waive for 3 years.

Me too. RM13k @ 3.99%PA. But remember that you have to pay ~RM1000 starting the next month. It's not paying starting after one year. If we take this into consider, then it's more than 3.99%.

If I borrow 13000, and I return 13518.70 after one year, then this is 3.99% PA.
But I need to return the money every month. Make it simple, 13000/12 = 1083.34. The first month I borrow 13000, after I pay 13518.70, then the second month I only borrow 11916.66.
Just like car loan compare to housing loan. 3.99% for housing loan is cheap, but 3.99% for car loan is very high.

RM150k per month, first-come first-serve

I paid income tax in ByrHASIL using VOX. Don't know can get cash back or not. Just trying even I know this card no cash back for government bill.

I also use CIMB CR to pay income tax for RM600, and use UOB VOX to pay RM1000. That's the maximum for both cards. CIMB CR should able to get cash back, but UOB VOX just try my luck.

I do not know about this. But I dont have Ambank credit card... How many percent cash back?