Can the tracker record my sleep if I forget to activate sleep mode?

No, you have to activate sleep mode for the tracker to record sleep data.

*credit to Sylvain of iHealth Labs EU

https://helpcenter.ihealthlabs.eu/hc/en-gb/articles/205766652-iHealth-AM3-Can-the-tracker-record-my-sleep-if-I-forget-to-activate-sleep-mode-