[Q] How to go back to a S2? - Galaxy S II Q&A, Help & Troubleshooting

Hi Everyone,
I am seeking some advice regarding our beloved Samsung Galaxy 2. I owed this phone in the past and after testing other devices, I am considering to purchase it again. Please kindly try to answer my questions:
1. I have Spinal Muscular Atrophy and I think the S2 is one of the lightest and thinnest smartphone on the market. Do you have any other devices in mind that could be suitable to my mobility issues?
2. I have purchased a few smartphones online (ebay and amazon) and always had difficulties to find one that is “truly” unlocked. Most of them were entitled as “unlocked” but would not work with my sim card. Do you have any advice on this issue?
2b. Do all S2s have the same processors/ram/features? Do you advise any S2 version in particular or all of them are fine?
3. I am interested in those new voice recognition features such as Ok Google/voice and my guess is that the most efficient and reliable versions of it are present on the latest Android versions such as Lollipop/is there any correlation between Android version and Voice recognition efficiency?
3c. Do you think it would be possible to install Lollipop on a S2 and how?
3d. Would it be a simple and “official” update or will it necessary imply a “jailbreak”? Knowing that I am definitely not familiar with this kind of process, are there accessible and straightforward tutorials for newbies showing how to proceed step-by-step?
3e. Would it slower the S2 to update it with Lollipop or create any other issue//conflict/flaw? If so, until what Android version can I update without slowing the S2?
Many thanks for your kind help!
Darkk.

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DarkkPhenixx said:
Hi Everyone,
I am seeking some advice regarding our beloved Samsung Galaxy 2. I owed this phone in the past and after testing other devices, I am considering to purchase it again. Please kindly try to answer my questions:
1.I have Spinal Muscular Atrophy and I think the S2 is one of the lightest and thinnest smartphone on the market. Do you have any other devices in mind that could be suitable to my mobility issues?
2.I have purchased a few smartphones online (ebay and amazon) and always had difficulties to find one that is “truly” unlocked. Most of them were entitled as “unlocked” but would not work with my sim card. Do you have any advice on this issue?
2b. Do all S2s have the same processors/ram/features? Do you advise any S2 version in particular or all of them are fine?
3.I am interested in those new voice recognition features such as Ok Google/voice and my guess is that the most efficient and reliable versions of it are present on the latest Android versions such as Lollipop/is there any correlation between Android version and Voice recognition efficiency?
3c. Do you think it would be possible to install Lollipop on a S2 and how?
3d. Would it be a simple and “official” update or will it necessary imply a “jailbreak”? Knowing that I am definitely not familiar with this kind of process, are there accessible and straightforward tutorials for newbies showing how to proceed step-by-step?
3e. Would it slower the S2 to update it with Lollipop or create any other issue//conflict/flaw? If so, until what Android version can I update without slowing the S2?
Many thanks for your kind help!
Darkk.
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1. Sorry no idea here.
2. By rooting your phone you could remove the branding and use any sim card
2b. The most common version of galaxy s2 is the international one gt-I9100. Depending on the year of when it was made there could be a slight difference in processor. Older processor need more voltage than the newer ones and might not be able to overclock as much as the newer ones. But if you don't intend to undervolt your phone this is unimportant for you. All of them work with 1.2ghz. Which processor type you'll get is some kind of luck I guess.
Gt-I9100 aside therealso are gt-I9100P and 9100g. I'm not sure but I think they work with same specs as the international one (1, 2 ghz and 1gb ram) but they use other hardware and thus it's not as easy to find custom roms like for the gt I9100 I think.
Furthermore there also is the galaxy s2 at&t version. If I'm right this the t mobile version of this phone. It also has the same specs like the other models (different hardware too) but the difference is this phone has no physical home button, which for me, looks better somehow.
I'd suggest to take the international one gt I9100 or the at&t version.
3. Official android version of the galaxy s2 models is jelly bean 4.1.2 which also is required by Google search and Google now. I assume it doesn't matter rather you have android 4.1.2 or 5 regarding the voice recognition.
3c. At the moment it's not possible to install Lollipop on a S2 but it may be possible in the future. You'll have to root your phone therefore and flash/install a custom rom based on lollipop.
3d. Like already mentioned earlier you'll need to root your phone in order to get past android 4.1.2. Depending on your phone model (2b.) It can be extremely easy or a bit more difficult. I'm just used to the international version gt I9100 which can be rooted with an app via one tap. That aside there are various step by step tutorials, as the galaxy s2 is a very popular phone.
If you'll root your galaxy s2 I highly recommend to Google emmc brick bug before doing so.
3e. All official android versions can become slow after some time, especially because of not removable, pre installed apps. With root you have the possibility to remove those and make your phone faster. If you intend to stay on official firmware you should update to the latest (4.1.2).
Talking about getting slower with higher android version is a bit difficult here. Theoretically with higher android version the phone will get faster....at least that's what Google says.
However as already said the galaxy s2 is stuck on 4.1.2. The only way to get higher are custom roms and those can be slow or fast no matter on which android version they are based.
For example cyanogenmod 10.1.3 is the fastest firmware I've had till now and it's based on Android 4.2.2. Jelly bean. Next there's for example aicp rom based on 4.4.4 KitKat. This version wasn't very fast for me. Another KitKat rom, NeatROM, however was faster than aicp although it has same android version.
It always depends on your personal phone, because each phone (or each galaxy s2 in your case) reacts a bit different to it's firmware and also on the way the developer made their custom roms.
You'll have to find out there
Sent from my GT-I9100 using XDA Free mobile app