Can someone please show me a difference between the old gamepass shop to the new one?

This is the updated version in this example, if you own the gamepass your cash will go up 1,000.

-----------------
--- Variables ---
-----------------
local Players = game:GetService('Players')
------------------
-- Gamepass Id ---
------------------
local gp= 5113033

game.Players.PlayerAdded:Connect(function(plr)
if game:GetService("MarketplaceService"):UserOwnsGamePassAsync(plr.UserId, gp) then
	for i, player in ipairs(Players:GetPlayers()) do
local BPS = player.leaderstats.Cash
BPS.Value = BPS.Value + 1000
end
end
end)

Developer Products:

local plr = game.Players.LocalPlayer
local id = 0 -- change "0" to a developer product

script.Parent.MouseButton1Down:Connect(function)
game:GetService("MarketplaceService"):PromptProductPurchase(plr,id)
end)

-- This example is for a GUI, you'll see examples of this on tycoons--

The old version I don't know much about, but I am more familiar with the newer method. If this answers the question you had, please accept my answer. If you have questions please comment and I will get back to you as soon as possible.