Is everything predestined or there is such thing as freewill? Can we change the lines on our palm? Is it true that whatever happens, there is a reason behind it. right time, right place? like me typing this asking you all...is it suppose to happen that is why it is happening..
You ever heard of naadi shastra or naadi leaves ...just in case you don't know ..it is said that everything is written on those leaves from your past to future..your previous births, present and your future births etc. What is your take on that? Is it reliable? Anyone ever got theirs checked??

I have been studying palmistry for years and i have seen the lines on my hand change, as well as the lines of my friends and family whose hands i check periodically.  You simply have to look at your hand, and you will see the lines on your hands change all the time.  Look at your hand while you are nervous, it will look different, look at it when you are playing sports, it will look different,  look at it when you are doing a task such as reading and it will look different.  Of course the lines wont change much during a day but how dark they are, which ones are dark, color of your hand and the lines, and even some changes in minor lines occur on a daily basis.  The lines simply reflects ones self, thus as you change, so will your lines.  

I have seen many dramatic changes in lines on peoples hands.  My sister used to have an island on her life line, now she doesn't, remarkably that also coincided with her facing a lot of domestic problems and resolving them.  My brothers fate line used to end at his head line, and now it goes well beyond that.  Again this coincided with him deriving more purpose and meaning in his career.  These are just some examples that i am mentioning.  

You are asking a very comprehensive question, one whose answer would take a very long time to come to any kind of firm understanding of the topic.  Is a man born to a rich family going to remain rich his whole life, while a man born to a poor family going to remain poor their whole life?  No the rich man could lose his money while the poor man could through effort or sheer luck make his way out of poverty.  Man has free will and the ability to create his future, and indeed he does create his future.  As it is written in the bible "that you sow, shall you reap."  That is also the primary tenet in hinduism or buddhism.  Thus the cause of anything can be found in the past.  

Thus, karma is not opposed to free will, but in fact karma is built upon such an idea.