Query about foreign exchange and foreign trade?

1.

What is difference between hedging and forward contract?

2.  Please explain about the cancellation and extention of forward contract and its implications on the bank-importer or bank-exporter dealings?

3. What is TT buying and TT selling rate?

4. what is recent "Exchange Marging" as per FEDAI in case of:

   i) TT buying rate

ii) TT selling rate

iii) Bill buying rate

iv) bill selling rate