Do alcoholic beverages prevent from praying 40 days i.e: prayer is not accepted or is this just a common misunderstanding? Most people who told me this didn't specify any scripture. Would you clarify please?

The meaning of not accepting the prayers of a Muslim who drinks alcohol is that his deeds are dispraised and rejected by the angles and he misses the reward for them. This happens if this person insists on committing such a sin based on the generality of the words of Allah the Almighty "Indeed, Allah only accepts from the righteous [who fear Him]." (Qur'an 5:27).

If this person repents, Allah will forgive him his sins. Allah the Almighty says,

Say, "O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah . Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful. And return [in repentance] to your Lord and submit to Him before the punishment comes upon you; then you will not be helped. (Qur'an 39: 53-54).

Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills. And he who associates others with Allah has certainly fabricated a tremendous sin. (Qur'an 4: 48).