Can Apple trace iPhone based on IMEI number?

No, Apple will not involve itself with any lost or stolen personal item in any way.

Without an internet data connection, no remote tracking software can work.

All you can do is look for it yourself.

Find my iPhone works through your iCloud account (it is a setting in your iCloud account's settings - the find my iphone app in the app store has nothing to do with making your device findable). If you did not have that setting enabled under your iCloud account, or the device does not have a data connection, it cannot be tracked.

nutan_bashte wrote:

When the phone was misplaced, data connection was not ON. But I have set up Lost Mode using Find My Phone. Will I get alert if someone (even after jailbreaking) connects to internet/voice line?

If it can be located before it is jailbroken it will go into lost mode as has been set. You should get an email saying so. Jailbreaking however can bypass many things so there's no way to know what it can or cannot do.

In switched on condition, if the SIM is removed, does it power down the iphone?

No. Removal of the sim does not affect the phone in any other than removing service. THe Phone will remain on but will dispaly the "No Sim" message in the top bar until one is inserted.

nutan_bashte wrote:

Can someone connect to new wifi even in locked mode?

Not unless the Phone is set to connect automatically to any unsecured Wifi network it finds. If its not set to do that you cannot connect to a Wifi network from the lock screen.

In current state, my iphone is not usable for layman user due to passcode. But my worry is if someone sells it to local stores where they can jailbreak to open the phone. Is there still any chance that Apple can track using IMEI / serial number?

No, apple cannot track a phone using an IMEI number. And Apple will nt get invo9lved in lost devices. The onyl way to track a phone is to use find my iPhone. THe IMEI number just identifies the phone but is not a means of tracking it in and of itself.

nutan_bashte wrote:

Can Apple trace iPhone based on IMEI number if its stolen and being used in different countries?

No. Again the IMEI number canot be used to track a phone only to identify it when it has been found. Your carrier can block the IMEI number so service cannot be activate it on it. Apple can do no such thing.

nutan_bashte wrote:

All in all, what is the possibility of tracing/getting the iPhone back? The phone is more precious for me than a diamond. So I am bothering you all with my post. Hoping for suggestions/solutions....

Unfortunately not very good. But if you had iOS7 installed on it at least it cannot be used unless the thief jailbreaks it and is able to remvoe iOS 7 from it.

However, all may not be lost, If you had your phone backed up which you should have been doing regularly to iCloud or iTunes you shouold be able to restore that to a new Phone and get most if not everything back.

Phil0124 wrote:

Unfortunately not very good. But if you had iOS7 installed on it at least it cannot be used unless the thief jailbreaks it and is able to remvoe iOS 7 from it.

Even if iOS 7 was removed the phone would still not be usable. Activation Lock is implemented in Apple's activation server, not on the phone. Any attempt to activate the phone, even with an earlier iOS version, will fail. And there is as of yet no jailbreak for iOS 7.

my iphone 6 plus is missing last week and it has no icloud account because it was new. someone stole it from my pocket. how can i track it down using IMEI. pls help me

Contact your local police. Apple cannot help you, and without find my iPhone setup in an iCloud account, there is no way for you to track it yourself.