Do I have to make a transaction to get airdrop, (currently the price is 25 DAI per transaction), or is it enough just to send 1ETH to the exchange office and return the coins back to my wallet?
You must have excess eth for the gas fee. Yes 25dai is their fee quite high so this is a risky trade for an airdrop but if the value of tokens that might drop to the wallet could have an immense value. Who knows this is still a speculation not really sure about the value and amount of drop it can give, can also have none. But there are plenty of bullish that there will be an airdrop.