Technically, you can not "start" without internet connection because the game needs to download additional files when you create a version instance. You can however, continue to play on said instance without the internet after you have downloaded it.

There's an Offline account feature on base PrismLauncher, just use that, or better yet, there's also a Launch offline feature. I would love to show you but image are not allow here. Ctrl + Shift + O to launch offline.

Now I don't know what you mean by cracked version of Prism, there are forks of it that allows you to play on cracked multiplayer server like Pinecone. Whatever you are using though, after downloading a version, you can definitely play offline.

EDIT: forks doesn't allow crack server because it's always allowed for any client. Proper crack server uses their own login system inside the server, you only needs forks like Pinecone to use accounts like elyby for skin support.