Your question is incredibly vague, I can only say three things about it, and those are this:
1. Yes, glitch city exists.
2. No there is no serious side effects of going there.
3. To go there, go to this site: http://www.ocf.berkeley.edu/~jdonald/pokemon/glitchcity.html
catch Missingno
there really isn't glitch city but if you put in a specific cheat of something, maybe you might come across glitch city. WARNING: glitch city may not have a Pokemon center due to the glitches...
its not catchable in red blue or yellow but you can glitch it up and get it.
no, you catch different Pokemon in yellow, you get ALL 3 starters, and theres no glitch in yellow. :)
Sure! There's Glitch city To get it go to http://www.ocf.berkeley.edu/~jdonald/pokemon/glitchcity.html There is a glitched up Missingo Pokemon (I dont know how to get that) There is a mew also!
No. Missingno is a glitch pokemon found in pokemon Red, Green, Blue, and Yellow.
nope
No-- but I think you can use the Action Replay, or there might be a glitch that can make you Pokemon over lvl. 100. In the Red/Blue/Yellow versions, a glitch (called the ZZAZZ glitch) will make your Pokemon lvl. 153.
cinabar island
It is only possible to get Weedle in Pokemon Yellow by either trading it from Pokemon Red or Blue versions, or use the Mew Glitch and battle certain trainers.
You can get Magmar in Pokemon yellow on the Nugget Bridge in Cerulian City. All you have to do is use the mew glitch without gameshark. go to Vermilion City and fihgt the engineer near the first snorlax. Teleport or fly back to Cerulian and head to the Nugget Bridge. Magmar will be waiting unseen.
The only way to get Mew in Pokemon Red, Blue, and Yellow is via the Mew Glitch, which you can find on Bulbapedia.