help!!

1. As long as you have their friend code and they're online, you can battle them. You can request a battle here: http://forums.supercheats.com/newtopic.php?forum=1792. Be sure to include your friend code, and when someone responds, include a meeting (time and date) so you guys can battle.

2. The Sinnoh Underground is a place located directly underneath Sinnoh where you can do many things. To get here, use the Explorer Kit anywhere as long as it's not in a building or cave. Whilst in the Sinnoh Underground, you can dig up spheres, fossils, stones, and many other items! You can also play Capture the Flag with a friend using the Nintendo DS's wireless feature. To make a Secret Base, you need to obtain a Dig Drill (or whate it's called) and use it anywhere you want. If you follow the Underground Man's directions, you'll eventually receive the Dig Drill. He's located in the house next to the Pokemon Center in Eterna City. Once you make a Secret Base, he'll give you some decorations to decorate your secret base with.

1: Let's see, if you have their friend code, know when they are going to be on, and are ready for a battle, then my answer is yes, you can battle them. But if you want to ask someone here for a battle, then you have to go to The Pokemon Battle Forum. So, that's really all there is to it.

2: The Underground, you do not know where it is? Dude, the Under-ground is... Well, underground! You can get to the underground from almost anywhere by using your explorer kit! There is tons of stuff to do there, you can meet your friends in the under-ground, play with your friends, dig up rare items, bury them, set traps for people to fall into, and even make a secret base! To get the Explorer kit, and all the other stuff that you need, go talk to the Underground man in Eterna City.