As we know that Spell check functionality in Draft space and Review space is being introduced in the 14SP4 version.
Can we do some configuration updates to make this feature available in Docs 14SP2?
No, that is not possible as you need an extra service "Trisoft InfoShare ContentQuality" on the application server to let Spell Checking work and that just is not there in 14SP2. It's supported only from Tridion Docs 14SP4.
Note: please note that Quality Check only supported in Draft Space not Review space.