Change fieldname 'name' and 'item_code' on Item doctype

Can I change field name ‘name’ and ‘item_code’ on Item doctype?
Is it going to trigger any error?

This is not a good action, such those two fields are linked in most doctypes!
Why you want to change them, you can change label instead if needed!

Because company where I woris doing a lot of changes and one of these is how item code is generated.

So after search I found rename tool but it does not work.

This is a screenshot of it.

And this is my csv file.

I am using:
ERPNext: v8.x.x-beta (780f11e) (develop)
Frappe Framework: v8.x.x-beta (8e5becf) (develop)

Ok, you want to change naming series, not field name itself
You can make this from Auto Name field in the doctype
To make your naming series you can do like this example

No, you misunderstood me. I want to rename an Item that I have already created. The AutoName applies when I create a new Item.

You can edit the name of the item by click on item name, then it allows you to rename it!

I know I can do that, but it will take a lot of time renaming one by one. That is why Rename Toll exists to rename multiple items. But it does not work for me.
An I am asking why.

Have you considered running a SQL file on the database that will perform the required renaming operations? Something like

 UPDATE `tabItem` SET `name` = 'newname' WHERE `name` = 'oldname';
 (... generate automatically based on the rename table ...)

Then run

$ mysql (database_name_here) < (file).sql

I thought of it, but I am afraid it might mess up things, that is why I want to use their tool.