Is the reward for congregational prayer and for praying in the mosque counted when one prays alone in the shade, far from the mosque, while hearing the voice of the preacher and the imam, and what is the maximum permissible distance for moving away in congregational prayer?

Your prayer alone outside the mosque is valid if you can hear the Imam's voice during the sermon and prayer, and this is an accredited opinion among some scholars. Your prayer is not invalidated by your being alone according to the majority of jurists. However, you will not receive the reward of one who prayed inside the mosque, and you should avoid doing so to avoid controversy and as a precaution for your faith.