For the recent Citibank Reward Visa card promotion where every dollar spent will earn us 8 miles, does it apply to shopee top up?

I dont have CRV but based on my other cards, yes. As banks used MCC to determine the rewards and cashback eligibility, it should be the same for most unless specifically excluded by bank.

However, an easy way to test out is to make a small amount topup. After you checked and make sure got points then you do lump sum.

Also, everytime before lump sum you should check again. Banks can change the terms accordingly. May work this month but not next month.