There is no Sinnoh to unlock in either game. If you want to access Sinnoh, you must buy Pokemon Diamond, Pearl, or Platinum Versions.
You can't, the only region avaible is Sinnoh.
unofrtunately, you can't unlock the hoenn or sinnoh regions in heartgold or soulsilver. but i hear that the Pokemon executives are going to come out with a game that encompasses all the regions soon. (I think it starts with the hoenn region, then goes to kanto, then johto, then sinnoh.
You have to see every Pokemon in the Sinnoh region. When you talk to the professor, professor Oak will show up and give you the national pokedex.
you hav to complete the sinnoh pokedex!
you have to see every Pokemon in sinnoh then go to professor rowan and he will give it to you
above the resort area which you unlock by getting the sinnoh dex
You unlock Silver Prints by beating the Frontier Brains in the Battle Frontier in Platinum.
you can get them away by seeing all 150 pokemon in sinnoh region and get the national dex and when you get the national dex you can unlock new areas such as spring path and full moon iland
She is the champion of the Sinnoh region. You'll need to beat her when you get to her. In certain places, she'll come see you to give you some things to help unlock certain Routes and towns. In Platinum she'll give you an Pokemon Egg.
well is´NT exactly a region, the Shinto ruins are localized in Sinnoh, and for unlock it you need to show an event Arceus to the old man inside the house of the Ruins of Alph, then the guy will lead you inseide the unown ruins and you will be transported to the Shinto Ruins.
you should be able to get an s.s. ticket to ride the ferry to the kanto region then from there you can collect the kanto badges to unlock mount silver where you can battle red/ash.