I’ve used LineageOS with microG on my Oneplus 6 for years — so happily, in fact, that I haven’t bothered with major updates since version 17 (Android 10). Oops!

Now I’ve been flashing updates to an older phone, and I might as well continue getting my daily driver up to date. I’m going to dirty flash my way up to the current version (21). But I’m rusty as all heck, and the upgrade instructions seem to have changed since last:

1. Back in '21 I recall being recommended to disable screenlock (fingerprint/PIN/pattern, etc) before upgrading. Is that still a thing?
2. With a/b slot devices it used to be necessary to flash ROMs twice or use a copy-partitions or simiilar zip file. The instructions make no mention of it, is that rolled into the upgrade package now?
3. Finally, is it safe to just upgrade directly from LOS/mG v18 to v21? Because neither LOS main or the mG branch seem to archive older versions but I’d hate to miss some system update or other.

All help is appreciated!

Edited for clarity: Please don’t offer suggestions on “better” phones or OSes — my question regards the above only. Thanks in advance 👍