does the train ticket has seat number ?

Yes, your seat number and ID No. or passport No. will be shown on the train ticket.

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Generally, all train of all classes have tickets with seat/sleeping berth numbers. If you get on the train and find someone already on your seat, show them your ticket and they will leave. Otherwise you may ask the conductor for help.

If all seats have been sold out when you are trying to buy a ticket, you will be asked if you accept a no-seat ticket. You are allowed to get aboard, but you'll have to find a spare seat yourself. If you're luck, there may be some kind people like to share their seats with you.