Can I ask OpenClaw to update itself

Short answer: possible, not recommended. The update flow can restart the Gateway (which drops the active session), may need a clean git checkout, and can prompt for confirmation. Safer: run updates from a shell as the operator.
Use the CLI:
openclaw update
openclaw update status
openclaw update --channel stable|beta|dev
openclaw update --tag <dist-tag|version>
openclaw update --no-restart
If you must automate from an agent:
openclaw update --yes --no-restart
openclaw gateway restart
Docs: Update, Updating.