“Premining” is actually a made-up word, that we've defined it as a creation of some coins, before the cryptocurrency gets launched. Almost all cryptos are premined, even Bitcoin. Satoshi was mining for a month, before he/she announced it on bitcoin.org. I just wanted to point you that, let's move on.

So you want to lock up a “premine”. To me, this sentence makes no sense, because of the definition of “premining” above. Can you give me an example of what exactly you want to do? When you ask for help on a forum, especially if it has to do with coding, you have to be precise.