No. It will cost money. Portal costs money. It was only free for a limited time.
You need steam to install Portal 2 Why not? It's free
You can buy Portal from Steam. Portal was free on many occasions but it is currently a paid product.
Portal or Portal 2 mods on Steam is installed by first Downloading it and extracting it. Then copy the map file into your Portal 2 maps folder which is Run the game.
I don't believe you can because the maps are only downloadable from the Steam Workshop, not the PS Store. I hope they have a way soon but for right now it is only for PC. If you bought Portal 2 new you should have a redeem code for a free copy of Portal 2 on Steam.
Sure
It is free on Steam until the 20th of September. Just go to the Steam store and search for Portal. It says it costs money but you can install it without paying. Enjoy it, it's a very good game.
Once in a while, Valve will have portal be free for a while.
Urm... you just buy Portal 2 from Steam and then play it...
The only way to get Portal for free is by illegally pirating it via certain sites. (Which I think that is a really, really, REALLY bad idea...)However, you can get a demo called Portal: The First Slice on Steam...
No portal 2 is the only game that does that.
On Steam it will cost $49.99.
Yes. Very yes. Portal was released as part of the Orange Box in 2007 and on steam. Portal 2 was released earlier in 2011.