Do you have API's for Market Data?
Subject to change, but you can try https://api.dydx.exchange/v1/markets which will update every few blocks.
Do you have API's for Making Trades?
Each trade requires sending a transaction to the blockchain, so it doesn't really make sense for us to have a trading API. We can't sign your Ethereum transactions using your private keys, so you would have to send us the signed Ethereum transaction. At that point, it is not necessary for us to have it: you should just broadcast it to the network.
Do you have API's for Placing Limit Orders?
Please check out docs.dydx.exchange