I think you are confused.
There are 2 types of unlock in WP7.
The first type is "Carrier Unlock" which allows your phone to be used on any network with any SIM card.
The second type, which we refer to it often here is "Developer Unlock" which means that your phone has the ability to install XAP files without the need of having to go through the official Marketplace.
From your case, I highly doubt your phone is "Developer Unlocked" from T-Mobile. It seems to me that it's more likely that T-Mobile used their own ROM of WP7, hence the presence of their apps.
Now to address your issues 1 at a time.
RenaldoTT wrote:if I plug in my phone it might update and become relocked.
It will only update IF you click the update the button in Zune should there be any update notifications. Not all updates re-lock your device, e.g. Pre-nodo to nodo update does not lock your device.
However, there are cases whereby UNAUTHORIZED phones which are illegally dev unlocked relock when syncing with Zune as Zune communicates with the MS server to check.
There are ways to prevent this. The simplest being to put your phone into Airplane mode whenever you plug it to pc. Another way is to edit the registry, but I won't go there since you are new.
NOTE:This does not apply if you purchase your unlock using Chevron WP7 Labs or by having a valid MS Developer account.
RenaldoTT wrote:how do I install cracked apps on this device
This is actually very simple. Simply do a google search for XAP installers. One of the most user friendly apps would be Tom's XAP installer. Google it.
After downloading it, you will need to have the XAP file of the game/software you wish to install on your pc.
Let's use PES as an example.
1. Plug your phone into your computer(Please refer what I mentioned above about unlocked phones if you do not wish to get relocked)
2. Start Zune
3. Make sure Zune detects your phone
4. Open Tom's XAP installer or any other XAP installer you would like to use.
5. Browse for the XAP file, E.g. "PES.xap"
6. Select it and load it onto your XAP installer.
7. Make sure to check that the XAP installer says "Deploy to Device"(This should be the default). If it shows "Deploy to Emulator", click on the dropdown box and select "Device"
8. Make sure your phone is NOT in lock screen and is at the home screen.
9. Click deploy on the XAP installer.
10. Wait for it to finish and unplug your phone
NOTE:This WILL NOT work if your phone is not "Developer Unlocked"