First of all, there are many differences attributed between CS1.6 and CS:GO. The most important thing to note is the engine; it's improved dramatically over the past 9 years (CS1.6 was released in 2003, CS:GO in 2012). Namely, CS1.6 uses the GoldSrc engine, which is a heavily modified Quake engine, and CS:Go uses the Source engine.
Second, CS:GO features drastically balanced gamemodes and weapons. Most notably, they completely changed the way Hostage missions worked previously in CS:S and CS1.6, and made it a lot more balanced for both sides. Some new weapons were added, and most of other weapons got a huge balance update (default pistols get a buff that puts them up to standard to other pistols, deagle nerfed).
Along with that, CS:GO also features a matchmaking system extremely similar to that of TF2, but it forms games based on a "combat rank", which helps to put similar players of similar skills in the same games.
Some other features are a complete UI revitalization, a more informative and easy to use buy menu, and an extremely polished user-friendly tutorial. Some minor things are the removal of flashlights (some servers have it with plugins), as well as getting rid of pre-defined loadouts.
Also included now are "weapon" skins, cosmetic variants of stock weapons that have no effect on gameplay but can do things such as track kill counts, be named as something else, etc.
Currently you cannot use WORKSHOP skins they way you would want (+ I would too!).The plan is that someday it will happen , or that Valve will be verifying some of these skins and they will be getting released gradually.
This is the case because if there was no restriction we would get nazi symbols and stuff like that on every weapon in the first hour.
You might be able to DL it and see it ONLY for YOURSELF but I am not sure if so and how.
But for sure you cannot use it so others can see it too etc..For now.
GAME ON.
Best Answer
Yes, you can trade it at any time. However...
If both accounts have an authenticator for at least seven days, and do not have any bans, then no.
If not, then yes as regardless of whether you own both accounts in a trade, all trades are considered as a "business" trade and thus is subject to standard trade restrictions:
Note: Escrow times start from the moment all sides requiring an authenticator action are completed. (You know; go to Confirmations > [...] > Accept?)
Reminder: You can have MULTIPLE accounts use one singular authenticator.
This support page provides some information about Steam trading restrictions., though it's missing quite a few of the specifics.