Probably, im not sure answer this im still research, read and learn about signal and GSM and others. Correct me if there is any wrong information (CMIW) I will answer your question. IMEI is a unique 15-digit number that is used for serialization on the device you are using, for example smartphones, laptops and hardware to see date purchase, device information, warranty, when the device is turned on or active and so on, In my country there are institutions from the government that can do this, for example "kominfo, police, provider, bea cukai" The Central Equipment Identity Register (CEIR) will help those whose mobiles are lost or stolen, as they will be able to inform the Department of Telecom (DoT) via a helpline number after filing a report with the police.

1. Can this site imei-tracker.com site do this?

No, and I have never tried with this (beware scam) I just try to see device details but not to the location only basic information

example

IMEI num : 355112????????
Result :
Model :iPhone 13 Pro Max (IPHONE 13 PRO MAX) A2643
Brand : Apple 
Activation Status: Activated
Warranty Status: Apple Limited Warranty
Telephone Technical Support: Expired 
Valid Purchase Date: Yes
Registered Device: Yes
Replaced Device: No
Loaner Device: No
Carrier/SimLock Info: HERE (FREE)
Find My iPhone: OFF
Blacklist Status: Clean
and other things 

you can see in my repository (imei check) if you want to believes please try on the site (imei-tracker.com) try itself

2. Can anyone track IMEI with a third party website or IMEI tracker service?

Maybe, you can track with sites or services that have collaborated with governments, operators and others. But this requires strict permits and authorization. Can't do something like that easily or without permission because it's about privacy

3. Tracking the phone number and IMEI is same method?

From what I've read and I understand these are related, Operators can do ISD, HLR, SRI-SM. SRI (sent routing info) for SM (sort message) is the reapon from HLR (home location register) to SMC (sort message service center) using tower triangulation (BTS) to find. You cannot ask the operator to provide you with a location report. Phone company or provider does all the tracking when someone calls your cell phone number, the cell phone system already knows where you are this is a built in function of the tower (BTS) Whenever there is a phone call, call details are recorded by service provider (operator) So when you call someone or receive a call all call related details like call duration, caller info, phone number, IMEI number and location area code will be recorded at the nearest cell tower You can read about Triangulation, Trilateration, Multilateration. Agencies, providers or operators and hackers (maybe) have the ability to do that

*IMEI pinning is possible when the stolen phone is activated (powered on). If the phone is not activated, we can deal with the final stages of the phone (last location) At the last stage you will be able to know where the phone was deactivated (powered off).

4. Can IMEI be changed? How?

Idk, I haven't done this in practice, but from what I've read it does, you can change your IMEI

https://www.cashify.in/how-to-change-the-imei-number-on-my-smartphone

5. How to track my lost phone without using IMEI and phone number?

Hmmmmm, i think spying (monitoring) apps which can be installed on phone, email like i cloud, find my phone and other, but if you lost phone you can try this procedure

- Prepare a copy of the IMEI number that you have saved.

- Contact the call center or operator according to the cellphone brand you are using or call the police.

- Tell them you have lost your phone and give them the IMEI number.

- After that, the operator will track if your IMEI number unit is found.

if your phone is stolen or lost, you should report it to your operator and police by telling them your manufacturer, model, imei number, color, some specialrecognizable details (if any), place and date where it was stolen and some other circumstances that could help them to find or locate your mobile phone

6. Is there hardware and software to track IMEI?

You can search itself :D

I can't answer in detail here because it might harm me or this forum, I can't answer for sure and in detail and I'm not 100% sure of what I wrote, if there's something wrong, please correct it. Thakns for visiting my github repo don't forget give it stars and share w your firends. You can read on this

*Note

My advice, don't trust IMEI location tracking sites, phone number track location sites. I don't know this in depth, if my answer is lacking or you still curious. You try to ask people like security forces, employee at the operator (provider), telco, gsm cell, RF. This is a tricky question for me. OSINT is not easy, moreover it includes signaling (SIGINT and ELINT) and others where we do not have full authority access to what we want to search for. Hope this helps, this is a recommendation from me that I've read in the past

- https://www.seminarsonly.com/Labels/Sniffer_for_detecting_lost_mobiles.php

- https://sci-hub.se/https://ieeexplore.ieee.org/document/7345408

- https://indianexpress.com/article/technology/mobile-tabs/imei-number-india-track-stolen-mobiles-phones-how-to-find-imei-what-it-does-5790035/

- https://sci-hub.se/https://ieeexplore.ieee.org/abstract/document/8769521

- https://sci-hub.se/https://ieeexplore.ieee.org/abstract/document/9012000

- https://en.wikipedia.org/wiki/Cell_of_origin

- https://forum.seccodeid.com/d/apa-itu-imsi

- https://commons.lib.jmu.edu/cgi/viewcontent.cgi?article=1013&context=master201019

You need call this he can help you 

There is hardware and software for it, I won't tell you but I will give you a little information about price of this device it is expensive you can buy a car to try it or buy an affordable price range but less features happy hacking

Every time you make a call, the details of the call are recorded by your service provider. Let us elaborate on this process. Your mobile phone is registered with the nearest mobile phone base station. If you move to another location, your phone will register to another tower. This process is called "triangulation" and involves determining the nearest cell tower based on distance, signal strength, tower capacity, and several other factors. See Wikipedia for more information.

So when you call or receive a call from someone, all the details related to the call such as call duration, caller information, phone number, IMEI number, area code etc. will be recorded in the nearest cell tower. This information is shared with service providers.

The police officer contacts his provider of services and provides all the details of the call. Cops themselves don't use software. There are currently some scenarios where call tracking is a little more difficult.

case

lost or stolen phone

In such cases, the SIM card is more likely to be replaced. So tracking by phone number is useless. Using a new SIM card will register his IMEI in the phone with the new SIM card number. The police will use her IMEI number to trace the call using the steps above. Alternatively, you can use an online tool such as Find Phone By IMEI to determine the phone's region by IMEI first. Then contact your local wireless carrier and provide the call details.

Phone is off

This is the most complicated case. If you turn off your mobile phone, no information will be passed. In such cases, police officers can only access your call history up to the time your phone was on.

Changing IMEI? The answer is yes you have to have more knowledge, experience and it is difficult to do 

Do they have access? or they have a vendor or developer to make it