In Revelation 5:8, and 8:3-4, we see that the Saints’ prayers are offered up before the throne of the Lord. The Saints are no longer limited by time or space, and so human limitations no longer apply to them.
As to veneration, you are close. In venerating Mary, for instance, we are only recognizing the honor that the Lord gave her when He conceived of her in His mind and created her expressly for the bearing, raising and serving of His only Son. In the 100s, Saint Irenaeus wrote of Mary as the “cause of our salvation” inasmuch as her obedience to God in saying yes to Gabriel undid what Eve’s disobedience did at the fall from grace.
As to veneration, here is a section from the catechism:
2132 The Christian veneration of images is not contrary to the first commandment which proscribes idols. Indeed, “the honor rendered to an image passes to its prototype,” and “whoever venerates an image venerates the person portrayed in it.” The honor paid to sacred images is a “respectful veneration,” not the adoration due to God alone:
Religious worship is not directed to images in themselves, considered as mere things, but under their distinctive aspect as images leading us on to God incarnate. The movement toward the image does not terminate in it as image, but tends toward that whose image it is.
For this reason, it is not sinful to have an image of Jesus, or to venerate a faithful pastor who is a servant of God.