我已阅读它是永久链接的，我必须恢复出厂重置设备以取消链接帐户 - 这是真的吗？
I linked my Gmail account to my tablet and I longer want it linked.
I have read that it is permanently linked, and I must factory reset the device to unlink the account - is this true?
Will factory resetting my device delete everything including pre-installed app, or will it be like new with my pre-installed apps intact?
First, the word "factory reset" might be a bit misleading -- as one can easily tell by your first comment to your question: If the device ships with Gingerbread (Android 2.3.x) pre-installed, and after a while offers an update to e.g. Ice Cream Sandwhich (Android 4.0.x) which you perform -- a factory-reset thereafter will not reset it to Gingerbread.
To understand what happens at a factory reset, you need to know some of the way Android's file system works. To make that easier to understand, I will abstract (and simplify) this a bit:
There are multiple partitions created on the storage of the device. A few examples include:
/system, which normally is "read-only". Here the Android System incl. its pre-installed apps reside
/data, which is "read/write". Here go all the user's data, incl. the apps (s)he installs
There are some more partitions, which I will ignore for this example. With a new device,
/system contains the Android system plus pre-installed apps, as stated above -- while
/data is empty. That's the "factory state", we could say. Now you switch your device on, and go through the wizard: creating/configuring your account etc. These data are stored in
/data. So will the apps you download from the playstore, etc.
A factory reset now will return your device to "factory state": it will wipe all data it can.
/datais read/write, it will get wiped.
/systemis read-only, so it won't get wiped. This includes the pre-installed apps.
/data, so they will get wiped
/data, including their settings and data -- so they will be gone as well.
As you can see from above description, a factory-reset will "unlink" the connected Google Account. In my eyes, that's like I want to delete a file: sure, when I format the entire disk the file is gone... So there must be other ways which keep your data intact.
At least in earlier versions of Android, there was a different approach (not sure if that still works, though). As a factory-reset as the "last ressort" would either delete all your personal data, it does no harm to try the following in advance: If it still works, great -- if it doesn't, you still can do the reset:
If this trick still works, your account should be gone by now; maybe even the wizard will pop-up again automatically.
One thing to keep in mind when changing the linked Google Account are your payed apps. They are bound to the account you've bought them with -- so they might stop working when that account is no longer there, and most will do so. If you no longer want to use your old account, you need to buy them again.
By pre-installed do you mean system apps, or do you mean apps that you downloaded of Google Play?
It is true that you have to reset your device to get rid of the first Google account you added.
System apps (that came with the phone) will not be erased, but their data will.
Custom downloaded apps (that you downloaded off Google Play and installed) will be erased.
It needs factory reset to get it off, is it true?
A factory reset will clear all personal data liked with your Google account and all other data, settings, and apps that you have downloaded.
Will factory reset delete everything including pre-installed app?
Your pre-installed apps will NOT be deleted. However, your data for those apps will be deleted! So the pre-installed apps will still be there, it will be like you are using them for the first time.
Factory reset is simply resetting your device to the original image of the current ROM.
This YouTube video is a good resource to learn more about factory reset.