Generally, no. Game mechanics only permit a player to Synchro Summon on their own turn. The only exception to this rule is the Urgent Tuning card which can be activated during your opponent's Battle Phase as well as your own .
Urgent Tuning
Attribute: TRAP
Property: Normal
Activate only during the Battle Phase. Synchro Summon 1 Synchro Monster. (Send the appropriate Synchro Material Monsters to the Graveyard.)
Now you can because since there was a new form of synchro summoning call accel synchro which allows you to summon one when it your opponents' turn at anytime on that turn but you must have the requirements on the field first before doing an accel synchro summon.
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Yes, you can, as a Synchro Summon is a special summon, you can perform a Normal Summon on the same turn as one or more Synchro Summons.
No, you do not 'tribute' the Synchro Material for a Synchro Summon. They are sent to the graveyard, not tributed. You can tribute an opponents synchro monster for "Assault Mode Activate!" to summon the assault mode monster from your deck.
Yes, of course. You are allowed to perform as many special summons in a turn as you've got the resources to do so, Synchro and Fusion summons are kinds of special summon.
No, a Synchro Summon is a kind of Special Summon.
Not quite. A Synchro Summon is a Special Summon. A Tribute Summon is the same as a Normal Summon, except that when you Tribute Summon you need to tribute monsters. Also you can Special Summon as many times as you want to in a turn, whereas you can only Normal Summon OR Tribute Summon once per turn, except with a card effect.