Revelation 20:10 says the Devil will be cast into ''the lake of fire'' and ''tormented day and night for ever and ever.''(KJV)....

BUT! If the Devil were to be tortured for all eternity, God would have to preserve him alive... the Bible says that Jesus will ''destroy him'' (Hebrews 2:14, KJV)

That doesnt add up... Only way for that to make sense is if one verse is talking about something happening literally and the other is talking symbolic...

Lets have a look at wot else gets thrown into the lake of fire...

Cast your eyes to Revelation 20:14 ''And death and hell were cast into the lake of fire. This is the second death.''

Do you see that? Death and hell were cast into the lake of fire. Can death and hell[Hades] be literally burned?

''The lake'' mentioned here is symbolic, since death and hell [Hades] that are thrown into it cannot literally be burned!

Have a look at Revelation 21:8 also thrown into this symbolic lake are those without faith and those who are disgusting in their filth and murderers and fornicators and those practicing spiritism and idolaters and all the liars. This lake of fire means the second death its not the same as the death from Adams sin where we can be resurrected, this death is irreversible, death from which there is no hope of coming back to life... completely destroyed forever.

This was meant for the Devil and demons. Now some humans who continue to follow him will also be gone forever.

In wot sense are those in the fire tormented eternally?
At times ''to torment'' can mean ''to restrain'' someone. Once when Jesus was confronted by demons, they cried out: ''Art thou come hither to TORMENT us[restrain us in the abyss] before our time?'' (see Matthew 8:29,KJV) Luke puts it.. ''And they begged him repeatedly not to order them to go into the Abyss.'' Luke 8:31, NIV)
So all those in 'the lake' will suffer the 'torment' of everlasting restraint, or 'second death'