Gibbs energy and Entropy In Gibbs energy equation:

$$\Delta G=\Delta H-T\,\Delta S$$

At constant pressure, 

$$Q=\Delta H\tag{1}$$

and we know that $T \Delta S=Q$ (reversible)
so finally 

$$T\,\Delta S=Q\tag 2$$

Putting values of Equation $\text{(1)}$ and $\text{(2)}$ in Gibbs energy equation ,
we should always get $\Delta G=0$ for a reversible reaction. ..

Why isn't it so? 

I don't know how to search it on Google; if anyone could give me a link or otherwise explain it?
Reason 1: 

while $T\,\mathrm dS=\mathrm dQ$ for a reversible process, this does not mean $T\Delta S = Q$

Reason 2: 

The term "reversible reaction" is unrelated to "reversible process".

Lame Reason 3:

Because your "always" statement does not repeat the "constant pressure" requirement assumed for $Q=\Delta H$