Bible Study for Brethren

Once Saved Always Saved? (Click the image to open the page for the topic)

Are we called/responsible to spread the truth to brethren or other souls if we know they are being deceived?
Can end times be postponed?
Is there a “requirement” for the devil to reveal himself in some way, no matter how small and insignificant the “signature” may be, is the devil required to leave a “fingerprint” of some sort that can be seen by the right person?