I'm reading this right now...I'm only about halfway through, but I'd definitely recommend it.
In my opinion, it is perfectly accurate to define Mandela as a terrorist. He may have been fighting for "just" causes (anti-apartheid), but ultimately he was a counter-government fighter. In his book, he specifically explains how the organization he created, Umkhonto we Sizwe aka Spear of the Nation, was meant to be the violent branch of the ANC, doing things the ANC would not do.Umkhonto we Sizwe planned and carried out terrorist attacks on government utilities and other buildings, all meant to disrupt the reigning Afrikaaner government. He said he preferred that lives were not lost, but many were. In addition, he also helped organize the training of Umkhonto we Sizwe members into a virtual paramilitary force with the possibility of a outright fight in mind (though this was never considered a serious option IMO). To the point about if the ends justifies the means? I would say sure, he got what he wanted, though he spent a good portion of his life in jail. However I would not say that the violence perpetrated by Umkonto we Sizwe was what caused the end of the apartheid regime, and would instead sight growing pressure from international powers (countries and businesses) as the biggest reason for the end of aparthied, again just my opinion.
What was South Africa like before? Well i'm just going to assume you mean early 20th century africa before mandela. Basically it was what Mandela was fighting against. The cities were very rich and completely dominated by white Afrikaaners. The lowly and unskilled labor was done by black africans, but they were not allowed to live in cities and had to commute long distances to and from work, for minimal wages. The africans had very little legal rights, and they had to carry permits with them indicating their right to travel toward white areas. Schools were almost always segregated, but a big point of contention was when the Afrikaaners wanted to make it so afrikaaner was the primary language taught in class rooms, indicating a complete culture domination by whites of black society in South Africa. Things like this and other problems really brought hate from the black communities to the whites. Basically things were very bad, and heavily against blacks. However, an interesting thing to point out is that Africans from other countries often tried to illegally immigrate into South Africa, with full knowledge of the existing apartheid, suggesting it was still better than most other countries. After Mandela, apartheid ended and equality was technically returned to South Africa, but still today there are massive gaps in wealth, most often lining up with race, showing that even though blacks are legally equal, they are still very repressed and weak.
I think this is more of an opinion question, so I'l just give you my take... He is venerated so highly because while he was in jail he basically became a symbol of the anti-apartheid movement, and many countries and celebrities often chanted "Free Mandela" and things of that nature, so he almost became the movement. Further more, even though his roots can be traced to violent, terroristic methods, his time in prison softened his image and left most people forgetting what he did to wind up in jail in the first place. When he was still in prison, he was meeting with the white leaders of South Africa and talking with them about potential solutions, potentially bringing him more fame, though I am semi-sure the meetings may have been in secret so I am not positive about that part. He also was the immediate favorite for president upon being released from jail and on a side note, kind of reminds people of the wise old, trustworthy black man stereotype, kinda in the same way people love morgan freeman.
If you are very interested in Nelson Mandela then you must read his book "A long Walk to Freedom": http://www.amazon.com/Long-Walk-Freedom-Autobiography-Mandela/dp/0316548189/ref=sr_1_1?s=books&ie=UTF8&qid=1386344290&sr=1-1&keywords=nelson+mandela
Also, if you are still interested about him I would suggest looking up information, on the ANC (African National Congress), Umkhonto we Sizwe, The Rivonia Trials, and anything that pops up alongside those things. I hope some of this will help, please feel free to ask me anything. All my information comes from my African Decolonization class last year (Props to Prof Merkel) p.s. I didn't source any of this stuff, but it is almost all in his autobiography, and I only wrote this to procrastinate for other studying, but it is accurate to the best of my knowledge.
This database is also great for African history both in general and anti-apartheid specific. : http://www.aluka.org/
Son, I don't even know what this "Chad" is. If you're interested in my life, I wrote an autobiography a couple years back. No secrets in the publishing business.