Does the bitcoin testnet3 network support Segwit and OP_CSV? As far as I know, Segregated Witness and OP_CHECKSEQUENCEVERIFY are the last features needed to be able to fully implement a trustless bi-directional payment channel, from start to finish. (Technically you don't need OP_CHECKSEQUENCEVERIFY, it just makes channels a lot better)

Does testnet3 support those features?

If not, is there another public development chain which has those features?
Yes, testnet3 supports SegWit as of block 834624.
Yes, testnet3 supports both OP_CSV and OP_CLTV.


You might also be interested to know that there is a segnet test network on another port number. See https://bitcointalk.org/index.php?topic=1453392.0 for more details.