TRAINS

I need to buy tickets for

Hangzhou to Suzhou , Suzhou to Shanghai , Shanghai to Huangshan and Huangshan to Hangzhou

As there is many stations in one place i am confused, i need to buy the bullet type, and there is North , South , East , West train stations , is it, which one should i buy

Can i buy it altogether when i reach Hangzhou next month, will there be enough tickets on the day?

ZEN