Some problems in usage of fillorkill

I have some questions in Core Protocol.
I want to implement the Order using fillorkill in the smart contract, not frontend

  1. can we use fillorkill of V3/V2 in the V4?
    If we can use fillorkill function of V3/V2 in V4 then which proxy we should use?
    exchangeV2 or exchangeProxy?
  2. maker is required and taker is optional.
    let’s say I have DAI, USDT in my vault, I want to exchange USDT/DAI to ETH.
    in this case, who is maker, taker? which is makerAsset, takerAsset?

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