Option and Promotion

[yhm]

I found this question before but didn't find the answer that I need
when using price modifier. The modification is written beside the option
let us give an example
I sell product where its price depend on its weight
if 1 kg is for 100$ so 500gm will be for 50$ and 250gm will be for 25$
when I use price modifier it write
250 gm -75$
and this confuse customers
I found questions about this and the answer was make the price 0 and hide it and use plus instead of minus
I made this and for a customer when the price is equal zero he see "according to weight"
but this made it not possible to make promotion or discount as it is made on a price equal 0
In addition,
I wonder if it is possible to make a promotion for only one choice
for example if I wanna make a promotion for quantity of 4 Kg to be sold for 90$
when a customer but a quantity of 4 of the weight 250gm he will get 1 kg for 90$ and so I won't sell any package of 1 kg
the last question
if I wanna make a promotion of buy 4 get 1 free is it possible and if I wanna give free sample of another product with the quantity of 4 is it possible
Thanks in advance

[Basara]

Hello.
You can set the quantity discounts https://abantecart.atlassian.net/wiki/spaces/AD/pages/10747906/Quantity+discounts

Please check the 3rd party extension to change the price display https://marketplace.abantecart.com/option_price_pro
Contact extension developer if any questions

[yhm]

I found how to do this without the extension
Thanks

[abantecart]

Please share your finding yhm.