Amazon Online Selling Business Query

Q-1- Amazon Online Selling Related Weight Issue Questions
I am selling product on amazon,
Amazon charge the shipping charges on the basis of basis of product weight
Amazon shipping Charges are as follows for E.g. They Charge 1Gram To 500 gram- Rs100
501 Gram To 1 KG- Rs150.
Now Actual product weight is 600 Gram
But my competitors who are selling the same product write 400 gram weight were actual weight is 600 KG. which charge them less shipping charges & they make the profit in this way.
As my competitors are using such tatics i not able to sale same product beacuse i write actual weight of product 600 gram .Amazon charge me actual shipping charge. Rs 150 for each order
I speak with amazon seller support on this issue where they told we cross check the weight but 99% they don’t cross check or neglect it. So Low shipping charged is been applied for competitors & high actual charged is applied for me as I write correct weight
So my competitors are using such benefits & selling the product in amazon at low cost & earning profit
To continue on amazon online selling I have only option to use same tactic where I can show low weight of products than actual weight than only I can sell at competitors price. Is its permissible to do so?

Q-2- Amazon Product Category Commission Charges Issue
Amazon charge the commission for the product depends upon Category but seller show their products in wrong category so low commission is charged due to it
I speak with amazon seller support team they told that if amazon find such fraud in their audit they will blocked the listing but it’s long time amazon is not taking action & listing of product is active.
Even if amazon blocked the listing they make new listing in same way so Low commission is charged. Their is no peanlity is charged so seller keep doing so.
Now I have no option but to do so as described above, Is its permissible to do so?

Q- 3- GST Saving Related Query.
I sale product on amazon the price of product is 500 but in invoice its showing product price 450 + GST 50 =500
Now I want to give 50 rs to government which I have collected from customer in the name of GST, but by adding additional bill from suppliers I can adjust 50 rs by alternate ways
By doing so I can save 30 rs to me & 20 rs I can give to government as GST. As I have collected 50 rs by customers in the name of GST but I am giving only 20 rs to government by using alternate technics.
Is its permissible to do so as I am give less GST amount to government but I have collected full GST amount (Rs50) with customer.