Does poor academic performance in the (2/3rd) semesters of a 5-year program matter if I catch up on it and find good work experience later?

Would that hamper my chances of working abroad?

Do firms in the UK/US emphasize on that? Also, if anyone who has been working in UK firms can, please help me out.

Says who? In the US, UK, Singapore, everywhere which is a developed economy only people with a fancy degree get doors opened. Does not matter what work experience you have. it is ridiculous to say that someone with a Columbia JD will have the same opportunities as a Brooklyn Law School JD with more work experience.

Clearly shows you have never filled up a foreign law firm application anywhere. If you actually tried filling up the application forms of some law firms in England, they would ask you if you had achieved, or were on track to achieve, a "2:1" or an "upper second class" degree (which mean the same thing), and if you didn't, they would say "You do not meet our minimum requirements". Some firms even specify minimum grade entry requirements on their website. The process that happens for many students at English unis who achieve their TC offer while they are still at university is that the law firm tells them that their TC offer is conditional upon them achieving a certain result in the remainder of their law degree examinations (which would usually lead to the achievement of an upper second class or first class degree) and certain marks in the SQE. A similar process would apply to Indian law graduates who achieved training contract offers, who would be made to do the SQE and perhaps for some firms the Graduate Diploma in Law (GDL) after their vacation schemes.

Again, if you actually had a clew of what you were talking about, you would know that there was a scandal involving an SQE provider in which many candidates were mistakenly failed in the SQE, because of some sort of marking system error on multiple choice questions. Those among the impacted candidates who had training contract offer conditions imposed by firms who had either accepted them directly, or after assessing them through a vac scheme, still to fulfil had their TC offers withdrawn by their firms (I don't know exactly how the scandal panned out in the end re those TC offers, but I do know that compensation was offered and those failure records were corrected).

Please, therefore, do not propagate this ill-informed nonsense. Actually understand and read up on what you are talking about.