ashiqkoyisseri wrote:Is it possible for me to get CAS from any universities and switch to a Tier 4?
Yes, but you could only apply to "switch" (apply in the UK) if it was for a PhD or other course at a higher level and therefore represents academic progress. If the course is at the same level, it's the sponsor's decision whether it is academic progress or not. If they cannot confirm academic progression on the CAS, you would need to make a new entry clearance application in your home country. If they can confirm academic progression you can apply in the UK, but it would need to be a variation of your existing application.
You have not said why you applied for further leave, or why you do not wish to continue with that application, but it does not sound like it was a Tier 4 application. The fact that it is not yet decided, and that you do not wish to pursue it, suggests it was an outside-the-Rules application or other application perhaps with no specific grounds or strong foundation. If you previously took such steps to try to stay in the UK without any specific reason, you could expect the Home Office to be doubtful of your credibility as a student, and that is reasonable.
Any future Tier 4 application is very likely to be subject to a very rigorous check of your credibility.
I do not give immigration advice. I refer you to Immigration Rules, guidance, other online content and to your sponsor.