Please find my answers inline:
1. Did 4 wrong answers among the first 10 questions affect my score?
Yes, this is possible, first 10 questions do play an important role in your final score as they set the base for the following questions.
2. After reviewing I could have got 3(out of 5) SC questions and 1 (out of 2) CR questions right. So how do I avoid silly mistakes in the real GMAT.
This can be avoided by the help of practice. The more you practice, the more familiar you become with the questions and lesser the mistakes.
You can practice the Official Questions from
OG, Verbal Review, Question Pack1 and also the Exam Pack1
3. 'A certain tropical island received', this was the other CR question I got wrong. The reason for this was that I didn't understand what 'This result is relevant because....'. How do I avoid such mistakes?
I am not exactly sure about your question here. If you can post the entire CR, that would help.
4. Even after knowing all the SC rules I was pathetic at applying the
e-gmat 3 step process in the test (If I had,I would have got 3 SC questions right)
This again reflects a lack of practice. Applying the rules should become an intrinsic nature. As soon as you see the SC, you should start thinking about the rules. Fortunately this can be achieved, but you need to practice for it.
5. With last 5 minutes remaining I had 1RC passage and 2 SC questions to be answered. How could I time my test so as to finish it in time.
Not completing the test attracts a huge penalty. Timing issues can be avoided by making a grid on your scrap book. Put does certain milestones in your test and identify the time. Write it on the scrapbook. Now try to follow it. If your are lagging behind, you can skip/guess intelligently a question to get back on time.
6. While in verbal section, my head was getting heavy (slight head ache). How do I overcome this?
This is again related to practice. GMAT is like a marathon. You need to prepare well for it and to prepare for a marathon, you need to run for 42 kms, before you compete in one. Same with GMAT, you need to sit for 4 hours during the mock CATs. Make sure you take the CATs along with AWA and IR.