びる(のびる) (VI) Stretch or physically extend – whether it’s a piece of silly putty, or a forest that extends all the way to the ocean, or days of summer that get longer.  Use this one for hair! 髪が伸びたね! You grew your hair out!   $$$
びる(のびる) (VI) To lengthen. Like 伸びる, but less often used. In fact, this 延びる is usually used only in one expression: 生き延びる (meaning, to survive a dangerous event, or lengthen one’s life)
ばす(のばす) (VT) To lengthen or extend (the life of a sick person)(the deadline) (your stay in a hotel) also, to procrastinate. More used with time.   $$$
ばす(のばす) (VT) To lengthen – more used with physical things:stretch your back, extend a collapsible umbrella/telescope/ admantium claw,  extend your talent by developing it.   $$$
(えんちょう) Two meanings: 1) an extension or prolonging, in time. 2) To extend a linear thing by building it longer. More official than just saying 延ばす.