I have some questions:
When will PRL go to mainnet (release wallet and change from token ERC20 to coin)?
DAGchain network is difficult to install and easy to hack. After the combination with blockchain would be better?
I'm not sure about the answer to second question, but I know that the mainnet is scheduled to be released in April. The team really honored their deadlines so I expect for them to honor this one too. It will probably be released closer to the end of April (at least that's how they released the testnet A and the testnet B).
You may have been mistaken. A blockchain combined with dagchain requires a separate system to manage. The ERC20 code is a way for them to mobilize for the ICO. I'm sure they will exchange TOKEN with COIN. Take a look at ICX, they did it.