As long as the card that summoned the token does not mention any restrictions, then yes, token monsters may freely be tributed for a summon.
Some do have restrictions set on them, for example, Sheep Tokens from Scapegoat cannot be tributed for a tribute summon, but could be tributed as the cost for a Special Summon.
not all tokens can be sacrificed. If it is indicated that a summoned token cannot be used as a tribute then it is not.
You can tribute a special summoned monster, yes.
If the token is considered destroyed by battle, then it will leave the field and cease to exist, like any regular token monster.
A level 7 monster needs two tributes; you can tribute a level 5 monster but must also tribute a second monster.
A level 8 monster needs two tributes, so you can tribute a level 6 monster but must also tribute a second monster.
Generally, Tokens do not allow themselves to be Tributed for a Tribute Summon (i.e. Scapegoat Tokens). However, there may be some cards that allow such actions, such as Dandylion.Incidentally, Scapegoat Tokens only restrict their use for a Tribute Summon. This means that it can be Tributed for the effect of a card, such as Cannon Soldier or Panther Warrior, as they require Tributes as a cost, not to Summon.For more information on the fundamental playabilities of Token Monsters, click on the "Related Link" below.
You do not remove the counter for the summon, you tribute Ancient Gear Castle itself. So imagine you have Ancient Gear Castle with one counter. You can tribute it for a Lv5/6 Ancient Gear monster - but since Ancient Gear Castle is now gone, it cannot gain another counter.
not all tokens can be sacrificed. If it is indicated that a summoned token cannot be used as a tribute then it is not.
You can tribute a monster when an effect instructs you to, or you need to do so as a cost. So you can tribute a monster for a tribute summon only in your own main phases, when there is no chain in progress. You can however tribute a monster for one of Enemy Controller's effects at Spell Speed 2, in either player's turn, in any phase.
Tribute is only needed for the monster's Normal Summon or Set (or Special Summon in special cases). Flip Summoning does not require any tribute at all, regardless of what monster it is.
You can tribute a special summoned monster, yes.
If the token is considered destroyed by battle, then it will leave the field and cease to exist, like any regular token monster.
A level 7 monster needs two tributes; you can tribute a level 5 monster but must also tribute a second monster.
A Level 8 monster needs two tributes, so you can tribute a Lv5 monster, but must also tribute a second monster too.
A level 7 monster needs two tributes, so you can tribute a level 6 monster but must also tribute a second monster.
A level 8 monster needs two tributes, so you can tribute a level 6 monster but must also tribute a second monster.
You only need 2, like any other tribute monster that's level is 7+