Do we see planet Venus every day? (Just before sun sets or Just after sun sets) throughout year? or some days we don't see it?
No. Some days Venus is an evening star, visible for up to a few hours after the Sun sets. Some days it is a morning star, visible for a few hours before the Sun rises. Some days it is so close to the Sun in the sky that we can't see it at all (or even actually behind the Sun).
Venus can also be seen in daylight, if it is above the horizon, not too close to the Sun and the sky is clear. You need to know where to look for it, though, it's only a little brighter than the sky.
Venus goes through a 19 month synodic cycle as seen from Earth, roughly:
- 8 months as an evening star
- 1 month passing in front of the Sun
- 8 months as a morning star
- 2 months passing behind the Sun
In any given month, Venus can be an evening star all month, be a morning star all month, be too close to the Sun, or pass from one state to the next.