To detect the nether star, in my opinion it is best to make an item sorter. This can be made to only accept one type of item (in your case a nether star). If you place a repeater against a hopper, it will generate a signal whenever there is an item going through it. You can use this item to control a command block.

The command to teleport someone to a given location (if you know the coordinates) is /tp @p <x> <y> <z>, with @p denoting the player who is the closest to the command block. You replace <x> <y> and <z> by the coordinates you want the player to teleport to. To clear the inventory of a player, you use the following command: /clear @p. In the same way as the last command, it will clear the inventory of the player who is the closest to the command block.

Source: https://minecraft.gamepedia.com and a 5 minute Google search

To detect the nether star, in my opinion it is best to make an item sorter. This can be made to only accept one type of item (in your case a nether star). If you place a repeater against a hopper, it will generate a signal whenever there is an item going through it. You can use this item to control a command block.

The command to teleport someone to a given location (if you know the coordinates) is /tp @p <x> <y> <z>, with @p denoting the player who is the closest to the command block. You replace <x> <y> and <z> by the coordinates you want the player to teleport to. To clear the inventory of a player, you use the following command: /clear @p. In the same way as the last command, it will clear the inventory of the player who is the closest to the command block.

Source: https://minecraft.wiki and a 5 minute Google search

To detect the nether star, in my opinion it is best to make an item sorter. This can be made to only accept one type of item (in your case a nether star). If you place a repeater against a hopper, it will generate a signal whenever there is an item going through it. You can use this item to control a command block.

The command to teleport someone to a given location (if you know the coordinates) is /tp @p <x> <y> <z>, with @p denoting the player who is the closest to the command block. You replace <x> <y> and <z> by the coordinates you want the player to teleport to. To clear the inventory of a player, you use the following command: /clear @p. In the same way as the last command, it will clear the inventory of the player who is the closest to the command block.

Source: https://minecraft.gamepedia.com and a 5 minute Google search

To detect the nether star, in my opinion it is best to make an item sorter. This can be made to only accept one type of item (in your case a nether star). If you place a repeater against a hopper, it will generate a signal whenever there is an item going through it. You can use this item to control a command block.

The command to teleport someone to a given location (if you know the coordinates) is /tp @p <x> <y> <z>, with @p denoting the player who is the closest to the command block. You replace <x> <y> and <z> by the coordinates you want the player to teleport to. To clear the inventory of a player, you use the following command: /clear @p. In the same way as the last command, it will clear the inventory of the player who is the closest to the command block.

Source: https://minecraft.gamepedia.com and a 5 minute Google search