Mystic, that page in the link needs updating.
Shawnthesponge here's how to do a teleport
set up the sector that you teleport from. give this sector an unused sector tag number. then give the sector the effect number 64- Trigger anywhere in sector, or any trigger like this one.
After that, create the destination sector. Give this sector another unused sector tag number.
After this create a sector outside where sonic can access (like outside the Thock barrier). give one line of this sector the action number 300-Trigger linedef executer continuous. Tag this same line with the number you taged the first sector with.
Give another line the action number of 412- Teleport player to tagged sector. tage this line with the same number as the sector you want to teleport to. After this, place the thing called teleport destination in the destination sector.
Viola, you got a teleport.