Gonna try this.
1) What is ScarfChomp short for?
Choice Scarf Garchomp AKA best scarfer ever
2) CeleTran is a nickname for an infamous combination of two pokemon that damned near resist every type together. Which two pokemon make up this combo, and which type(s) do they not resist?
Celebi and Heatran. The only type they don't resist is Rock.
3) For some reason, my opponent keeps yelling in the chat that "Your Ferro is no match for my SubRise Zone". What is he talking about, and why should I be vary, especially if my main way of taking out steels is by using EarthQuake?
SubRise Zone = Substitute + Magnet Rise Magnezone. By using Magnet Rise, Magnezone is immune to Ground type moves for a few turns. This gives it a free Substitute because it's only fear is Ground type moves against steel types and Heatran
4) Why is it in general not the best idea to put a Focus Sash on a pokemon that doesn't lead off in a battle?
Since entry hazards like Stealth Rock exists.
5) I have a Lucario with the following moveset:
SD/CC/ES/BP. Identify the moves, and give the set a fitting nickname.
Swords Dance/Close Combat/ExtremeSpeed/Bullet Pawnch. Swords Dance Physical sweeper I guess?
6) My opponent used the move Gravity a few turns past, and is currently using a Mamoswine. Why would it be a bad idea to switch my Bronzong into it, which otherwise would wall its STABs completely?
Cause Gravity grounds Bronzong and makes him vulnerable to Ground type moves.
7) Why is it in general not necessarily the best idea to put a lot of Life Orbs as held items on a team with Tyranitar?
Cause sand storm deals damage to non Steel/Ground/Rock type Pokemon, so the Pokemon loses a LOT of health in one turn.
Decipher the set names;
1) NP MixApe -Nasty Plot Mixed Infernape
2) TrickScarf Rotom-W -Choice Scarf Rotom-Wash with Trick
3) SDef SD Scizor -Specially Defensive Swords Dance Scizor
4) CM Rank -Calm Mind Rankurusu/Reuniclus
5) BU Croak -Bulk Up Toxicroak
6) SD BP Scor -Swords Dance Baton Pass Gliscor
7) Air Balloon Tran -Air Balloon Heatran
8) AgiliGross -Agility Metagross
9) DD Bulky Gyara -Dragon Dance Bulky Gyarados
10) MixMence -Mixed Salamence
11) SD YacheChomp -Swords Dance Yache Berry Garchomp
12) JelliTaunt -Jellicent with Taunt
13) TR Rank -Trick Room Rankurusu/Reuniclus
14) QD MSun Volcorona -Quiver Dance + Morning Sun Volcarona
15) CB Azu -Choice Band Azumarril
16) SD RP Terra -Swords Dance + Rock Polish Terrakion
17) SubSplit Gar Substitute + Pain Split Gengar
18) NP Luke -Nasty Plot Lucario
19) Specs Lati -Choice Specs Latios (Not Latias since it's inferior when it comes to Choice Specs)
20) Double Dance Dra -Dragon Dance + Rain Dance Kingdra
21) RS Starmie -Rapid Spin Starmie
22) TechniTop -Technician Hitmontop
23) CB Meta -Choice Band Metagross
24) DD Babiri Tar -Dragon Dance Babiri Berry Tyranitar
25) SubSeed CM Bi -Substitute + Leech Seed Calm Mind Celebi
If you enjoyed solving these small tasks, I might write up some more.. ;)