i want to know if T1 and T2 relaxation time is infinitely long or short than what will be the effect on spectra?
I recommend you read Prof PJ Hore's oxford chemistry primer on NMR to double check this, but...
It is because you have a fourier transform, so I think (double check) that if you have an infinitely long relaxation time then you will have a perfectly sharp peak and if it is infinitely short then you have a really broad peak.