Hi!
Stall is an aerodynamic phenomena and has NO relation with CG position... BUT:
1- A aft CG (tail heavy) helps to reach high AOA, so stall can ocurr due to High AOA
2- An Fwd CG (nose heavy) can even be helpfull for avoiding stalls because plane can reach what we call "Trim"... the pitch moment due to the heavy nose is too big, so the tail pitch moment (considering maximun deflection) is not enough and AOA "stops" growing up before stall appears. This is a rare situation but could happen in some planes...

Conclusion: CG position can determine whether the stall AOA is reached or not (in most planes this point is reached); stall is an aerodynamic phenomena.

About tip stall: appears only in tapered wings because the tip chord is smaller so stalls before the root choords. The "perfect wing" which stalls completely at the same time is elliptical (like supermarine spitfire) while non-tapered wings tipically stalls from the center to the tips (named "safe stall"; all trainer stalls like this...)

Hope my comments are usefull to all...