Yes, you should be able to play the test realm/client using a trial account.
Yes you can.
Yes, you are able to play the PTR on WOW by using a 10 day trial account without any in-game restrictions.
No, your account will simply be suspended until you add additional game play time to your account.
No, the trial account is the only way to play the official live servers for free.
There are trial accounts that allow you to play for 10 days to try WoW out but that's it.
For most private servers you have to make your own account on the server's website.
It depends which trial you refer to. In the demo account (free forever) you only get one single human character and if you make any other characters your account deactivates and is turned into a trial. The 14 day trial allows you usage of any race but expires after 14 days. You can play a dragon on the 14 day account before having to pay for the game.
You can sign up for a trial account, which will give you 10 days to play for free. Other than that, there is no way to play WoW free.
Your WoW files are never deleted unless your computers crash, or the world ends, etc. Your free trial account stays inactive until you pay to play it.
In WOW (world ofwarcraft) there are different realms that you can select to play on. You can have a total of 10 players on each realm and a total of 50 characters across all realms. There are different types of realms too. There is a PVP realm (player vs player). There is a RP realm (role-play). There is a NORMAL realm (no special rules). There is a PVPRP realm (Player vs player / role-play).
To get the free trial account just sign up for a free battlenet account and download the client. This will allow you to play as many characters as you want up to level 20 with no time restriction. To play the full version of the game free is not possible, you have to pay to play.
Realm of the Mad God is a free-to-play MMORPG. However, you do have to pay for realm gold, the in-game currency, if you want convienence, like dungeon keys instead of finding them, backpacks instead of another account to store, and loot drop and loot tier potions instead of sinking more time into this game.