Asked im passed from 12th cbse board in 2011.and then im pursuing my b.com.frm sol du.but i wnt to admission in b.tech.pls help.

But i dont want to take admission in polytechnic (diploma course).can i do 12th again from science without appearing 11th .from any board or ignou or nios.if i will do my 12th from open the i was able to take admission in b,tech (regular)pls help me im so glad of u.and also tell about age limit