click the B button to shift between 2 gears
you have your battle mode set to "set"
Pokemon Diamond and Pearl both have set of Pokemon that they catch. For example Diamond gets stunkey and pearl gets glameow.
On the pc in the pokecentre, if you select a pokemon, then there will be an option to set it free,
The entirety of Pokemon Pearl and Diamond is set in the Sinnoh region. There is no way to revisit any of the other Pokemon world regions.
the time on your ds in the nighttime set
The Mach Bike is faster than the Acro Bike, and the Mach Bike allows you to go up slippery muddly slopes whereas the Acro Bike doesn't. Also, although you can ride the cycle path on an Acro, you can only set a record speed on a Mach Bike, because the Acro is much slower/easier to manouvre.
you click on the trap and press set
I do not believe there is, but i MIGHT be wrong. Sorry :(
Go to your key items, then select your bike, then set to register, that way every time you press select you'll be on the bike and then you can just ride.
you don't it is only avalible in pearl, diamond, and platinum.
you need to get a poketch that has an app for the time set to you ds
You can't. Sinnoh is only available in Pokemon Diamond, Pearl and Platinum versions which are set in sinnoh.