How do i do this to badges...

For instance, in Asimo3089's Coastline highway, when you collect all badges you get an in game ro-tercycle, how would i do that to my game, a reward for badges?

BadgeService has a method that lets you check if a player has a badge.

local player = -- player we're checking
local badgeId = 3249234234 -- ID of the badge

if game:GetService("BadgeService"):UserHasBadge(player.userId, badgeId) then
	--do stuff
end

So you'll have to create a script that checks every time a player spawns to see if they have all the badges. If they do, then you can act on that information.