Intake Valve - 4 Cylinder Engine

Q. In a 4 cycle engine the intake valve begins to open at?

The cycle begins at Top Dead Center (TDC).
A cycle refers to the full travel of the piston from Top Dead Center (TDC) to Bottom Dead Center (BDC).
At Top Dead Center (TDC) the piston is farthest away from the axis of the crankshaft.