Welcome to CE, #-Link-Snipped-#. Following are the answers to your questions -
1. Yes, you can make a career in software testing irrespective of your engineering discipline. While most of the companies would accept you there are a few companies that'd recruit only candidates from CS/IT/CE background. So make sure that you check the eligibility criteria before applying for the job.
2. You will need a lot of logic, common sense and ability to evaluate things critically. Everything can be learnt on the job. But to make an entry, you should equip yourself with the knowledge of-
- Operating Systems
- Common software tools and programs (Excel, Word etc.)
- Software testing in general. Watch videos, read books and blogs and participate in discussion forums and gain as much knowledge as you can about software testing. If possible, become an active QA in any of the ongoing open source projects. That'd give your resume a huge boost!
- Why are you restricting yourself to C? Nothing should stop you from playing with Selenium and teaching yourself PERL programming language.
3. Start with manual testing. Read about various testing terminologies and concepts like Why is testing required, what is manual and automation testing, what is a bug, what is a bug life cycle, its stages, what are the tools used in testing et al. Take some action than sitting idle and confused. The following discussion on CrazyEngineers might be a very good starting Point:
<a href="https://www.crazyengineers.com/threads/software-manual-testing-interview-questions.40153">Software (Manual) Testing Interview questions</a>.
4. ISTQB is one of the popular certifications. Focus on one and get yourself certified if you can. That will be a big step in the right direction.