I tried to look up the legacy version of the Ice Devil today, and I was surprised to see that it wasn't listed. I tried both the app and the website. I haven't confirmed any other specific omissions with 100% certainty since I don't remember every monster perfectly, but I'm certain that the Ice Devil was changed and the legacy version removed.

I have a couple of theories as to why this bug might have occurred. Firstly, the Ice Devil is from the Monster Manual (and the Basic Rules) rather than from Volo's Guide to Monsters, so perhaps MM entries were overlooked when adding legacy content back into the database.

Alternatively, since the Ice Devil is shown as being from the Basic Rules, it's possible that the usual guarantee that owners of a legacy source will have access to legacy content might have been overlooked for a free source. However, since all monsters in the Basic Rules are also in the Monster Manual, which isn't free, I'd greatly appreciate it if legacy versions of monsters from the Basic Rules could be put back into the database. If you don't want to clutter up the basic rules with legacy content, you could always list the legacy versions as being from the Monster Manual instead.

Whatever the cause, I'd love to have access to the legacy version(s) again. It can be relevant for deciding whether to treat something as a spell in cases (such as the Ice Devil) where spells were replaced with spell-like abilities.

Thanks for your time!

I just checked and there are three versions of the ice devil, the one from the basic rules, and two variants from the Monster Manual. It has not been updated since then.

https://www.dndbeyond.com/monsters?filter-type=0&filter-search=Ice devil&filter-cr-min=&filter-cr-max=&filter-armor-class-min=&filter-armor-class-max=&filter-average-hp-min=&filter-average-hp-max=&filter-is-legendary=&filter-is-mythic=&filter-has-lair=