I have two theories about what your asking if your talking about the player models when people die such as ragdolls, or your own player model.
Death ragdolls : reason they disappear is that you might not have an up-to-date graphics card software.
Your own player model: your computer is screwed. sorry cant answer that.
You Dont
No. Online games dont have cheats so the games are fair. you can cheat by having a aimbot but then you would be gay.
they only appear to rescue dugtrio from drowning in the sea but after that they dont do anything else
Even though its always over priced by morons who dont know pricing on tf2 items, it goes for 2 buds
i dont know but the second one is magma
there WAS a command item_found and it was fun but valve removed that command but there can be other way to do that but i dont know how
Wear the same gear as the guards so they dont suspect its you.
you dont
No you dont
i dont kow
plants dont appear, numpty, they grow :)
you dont, they dont exist