Must investments under DBS multiplier be made using that same account?

I have just opened my DBS multiplier account. However, my Vickers account is linked to another DBS multicurrency account and I can’t seem to change that. Does it count towards hitting the interest tiers for DBS multiplier if I invest via another account? Also, is any settlement mode (e.g cash, cash upfront) fine? The website states “ Trades can be settled using cash or Supplementary Retirement Scheme (SRS).” so I am not sure if cash upfront can be used.