Don't get too hung up on Oct. 23 in this context. You have a year from when the new database comes online to register stuff. There's literally no way for the state to know when you engrave the serial number. Yes, pick anything you want that's A-Z, 0-9. I believe you cannot use any special characters (&%!@#$, etc.) or any non Latin alphabet characters. You can use spaces and dashes on the engraving, but they're not part of the serial number. But for sure A-Z, 0-9 is safe.
I don't know if we'll be required to engrave a model and manufacturer and caliber with the serial number, or if a serial number is good enough. Perhaps
@pastera or
@CrackPot will have some insight.
You don't. Unless you want to eFA10 it, but why bother? The eFA10 system will be gone in a couple months.
Funny thing: The actual current law as written does not allow for "registration" using the eFA10 system. It explicitly says, "in writing", unlike the sale part of the law where it explicitly says, "online portal"