Does a great distance invalidate the prayer if I stand in a row that has no barriers, while the rows in front of me have barriers and pillars separating the rows, and should I stand next to a person standing in a row that has barriers?

Distance between rows in the mosque does not invalidate the prayer, and following the Imam (i.e., congregational prayer) is valid in the mosque regardless of distance or not seeing the Imam and those behind him, as long as the worshipper hears the takbir, because they are all in the place of congregational prayer. And closeness of rows is better than their separation, due to the saying of the Prophet, peace be upon him: "Straighten your rows, bring them close together, and align your necks." And it is disliked for worshippers to pray between pillars unless there is a need.