Is one who utters words with a sound and an infidel meaning, while intending the sound meaning, considered an infidel if the listener understood the infidel meaning and apostatized? And is the apostate who invited others to disbelief, then repented and did not invite them to Islam, sinful?

If someone utters words that could be interpreted in a valid sense or a sense of disbelief (kufr), and they intended the valid sense, then they do not commit an act of disbelief. However, they must deny the apostasy of anyone who understood their words in the sense of disbelief and clarify their true intention. If someone called for disbelief and then repented and embraced Islam, their Islam is valid, and they are not required to call back those who disbelieved because of them. Nevertheless, calling these people back falls under the category of da'wah (inviting to Islam) and enjoining good, and it becomes obligatory if they are the only one who can do it.