one of the limitations is that we can get only 12 continuous hours per session. Is there any limitations for the usage for GPU and TPU?
Yes, you can only use 1 GPU with a limited memory of 12GB and TPU has 64 GB High Bandwidth Mmeory.You can read here in this article.
So, if you want to use large dataset then I would recommend you to use tf.data.Dataset
for preparing it before training.
If you want to use GPUs you can use any TF version. But for TPU I would recommend using TF1.14.