Light it says light!!
There is no place known as Unown Ruins, but you can find Unown in Solaceon Ruins in D/P/Pt and Ruins of Alph in HG/SS.
By Symbol I assume you mean 'Unown' the symbol Pokemon. To get them in Ruby/Sapphire/Emerald, you have to trade them from FireRed/LeafGreen, Diamond/Pearl/Platinum, or HeartGold/Soul Silver. In FR/LG they are on Seven Island in the Tanoby Ruins. In D/P/Pt, they are in the Solaceon Ruins near Solaceon town. In HG/SS they are in th Ruins of Alph off Route 32.
Pokemon black and white :D
no, you can't
It depends if you like the original Pokemon or the all-new Pokemon but ss and hg have more Pokemon but b/w only have 152 Pokemon, i am glad to help
You can't go to Hoenn in Pokemon HG/SS.
You can't find registeel in Pokemon HeartGold.
You may only clone Pokemon in Emerald, but you may own as may of the same Pokemon as you can (bearing storage space in mind). Therefore, you cannot clone Pokemon on "Pokemon Heartgold" (HG) or "Pokemon Soul Silver" (SS).
i mean i was really think if it is exis in pokemon hg and ss
You cannot trade a Pokemon from the 5th generation to the 4th generation or below. Getting Pokemon from Black/White to HG/SS is impossible. You can migrate Pokemon from HG/SS to Black/White though.
it's a Pokemon game Heart Gold
no he does not evolve in Pokemon hg or ss