I understand this community can be a bit unorganized and confusing so I'll give you my process for rooting and installing custom firmware (there are other ways, but this works for my AT&T Infuse 4G SGH-i997).
First of all, no one uses ICS on the Infuse. There is a ROM, but it's underdeveloped because JB came out so quick. You will need to flash it to get to higher operating systems, but it is by no means a daily driver. Even JB is a little buggy compared to KitKat on the Infuse these days.
The first thing you want to do is root your phone and get a custom recovery.
There are more than a few options for rooting, but I prefer using ODIN (as I understand it, this is the tool Samsung uses to restore soft bricked phones). So this is a good thing to know how to do, in case you ever do soft brick your phone, you'll know exactly what to do.
Read the ODIN
instructions in full as I will only briefly explain.
You're going to have to install Samsung drivers.
You'll be using UCLB3_Unbrick_root_1.1.zip. If you used UCLB3_Unbrick_1.1.zip it would just get you back to stock GB with no root added.
To put your phone into download mode, first turn off your phone. Plug a usb cable into your computer. Then with the phone off, hold down both volume buttons and plug the usb cable into your phone
. A warning will come up and you push volume up to accept, realizing that you can easily soft brick your phone if you loose power or unplug during a download
Once downloading is done, the phone will reboot and you'll be disappointed to see that nothing has changed. Except one small thing, you are now rooted and you should have an application called SuperUser that will allow you to do nifty and also dangerous things.
Now follow this step in the ODIN instructions to add the custom recovery (CWM = Clock Work Mod):
The version with root works exactly like the above version, but adds root. To add CWM recovery to the rooted version, download a custom Gingerbread kernel from HERE or HERE and flash the zImage using SGS Kernel Flasher (found in the Play Store) on the phone. If you go this route for root and CWM, your Custom Binary Download counter will not show any custom binary activity.
If you follow the link in the second "HERE," you'll get the kernel I prefer since it was most recently updated. Scroll down the downloads section and grab "2013.04.30-CWM-Synthesis-1.2Ghz.zip." (1.2Ghz is stock for our processor, anything higher will be overclocked which I don't recommend).
Extract that and grab the zImage file in the update folder. You're going to copy this to your phone in a second.
But first you need SGS Kernal Flasher, you can get it off the playstore, but I despise having to log in to an OS I'm going to write over in less than a minute so I download the APK from here
. Hopefully you know how to install APKs from your SD card and that you'll have to check install from unknown sources.
Now flash the zImage using SGS Kernel Flasher. Your phone will reboot and hang on the Samsung logo and a creepy voice is going to tell you about how she's partitioning your phone and installing Voodoo lag fix. This is normal. Eventually your phone will reboot back into GB and you'll be ready to flash any ROM of your choice by rebooting into recovery.
You reboot into recovery by holding the volume up and volume down button while powering on the phone
. This is different than download mode and will take you do a new screen that you control with the volume keys.
You'll be using this to put new software on your phone.
Now you can bassically follow the instructions for getting to CyanogenMod 11 (Kit Kat)
The first bullet is what I just explained in detail.
Note that I didn't include the links in these instructions, just follow the link above to get to the original post.
Obtain CWM, this can be done using Jscotts Odin back to stock (Follow instructions and use SGS kernal flasher to obtain CWM)
Run Qksters IMEI backup script here
Make certain you are on ICS, this can be done by flashing Entropy's CM9
It is recommended now that you remove your SD Card
CWM: Wipe Cache / Factory Reset
Install ROM: Scroll down for downloads sectoion
... The package will start to install..
... Phone will reboot into the install screen again...
... Continue to install [Automatically] If not manually flash again
... Phone will reboot again and be at the recovery screen...
Install Gapps: Here - Working swipe!
CWM: Wipe Cache Partition
CWM: Advanced/Wipe Dalvik Cache
To be clear, when you flash a ROM, it won't be like flashing the zImage (that was just to get custom recovery). To flash the CM9 ROM or Qksters IMEI backup script for example, you leave the rom in the .zip file and simply put it on your SD card. Once in the recovery screen, you select "Install Update from ZIP" and navigate to the particular ROM you wish to install.
Also after updating to a higher version of Android, your phone will sometimes hang on the install screen for a long time. If it does for more than five minutes, it's safe to pull the battery and try flashing again (and sometimes necessary).
After flashing Entropy's CM9, you will be on ICS, you can use if you want but I don't advise it. You should continue with the instructions and update to KitKat after getting to ICS. I recommend Scott's CM11 (what I linked you to) or Scott's BeanStalk (find it in the Android Development Section).
Lately I've been using CyanFox
and I have to say, it's the most stable ROM I've used in a while.
If you have any questions about this, feel free to ask.
Best of luck and happy flashing,