I9300 stuck in bootloop , Cant enter Download or Recovery

Hey,
I got 2 X Galaxy S3 I9300,
and they both stuck on bootloop, I can enter download mode but after 2 sec it's bootloop again and i cant change rom,
I try to enter recovery mode and it's dont work, it's show me the samsung logo and again bootloop,
i tried to remove the battery and put it back and the phone turn on alone,
It's mean that i need to replace the power botton?
Any solution?
Thank you.

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I took RECOVERY but it did not enter

I'm new here, sorry if this is not the right place or something like that.
Sorry for my english, I'm not that good and it's not my native language.

I took RECOVERY [CWM_4.2.2_ODIN-s2vep.tar.md5] my phone after I installed (with odin) I try to log on to RECOVERY but it is not entered. It shows me the logo of Samsung, every 10 seconds this flashing it after 5 minutes and then it returns to normal (the phone itself) ... What am I supposed to do? I want to install a root and rom ...
I can go into downloading and to the phone (regular)

Device: galaxy S2 plus
Model: I9105P
Android: 4.1.2

help please

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how to enter the recovery mode in xperia s modified without root?

(sorry for my terrible english) I have a xperia s, and recently modified the rom for lollipop 5.1, only am I unable to root the device, it gives error in every attempt and method. I tried to enter the recovery mode, but in every way I can not. I wonder if you have any way to get into recovery mode so I can install the binary supersu, or if you have any way to install root without an error occurs.

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[HELP] Cannot enter usb host mode

Hello everyone,
after a failed attempt to replace my Custom rom with a RUU rom (BIG MISTAKE - flashing procedure stopped at 5% with ERROR [294] : INVALID VENDOR), the phone stuck at the bootloader screen (and I think that this is normaI) but there is no way to enter the usb host mode (by holding camera + volume down + power) in order to re-install HSPL (gold card) and flash a Custom rom again. Seems like the Usb mode has been locked in some way. Is it normal?
Phone buttons are working (I tried to enter usb host mode before starting flashing attempt and I did it).
Here's some information from the bootloader screen:

PI39110
SPL-4.6.175006.2 (140733)
eMMC SMS 15028MB, F: PA32
TOUCH A1(F:81, ID:1, V11, B:F8)
RADIO-17.500608.27

I really don't know what to do... is there a way to have my phone working again?

Thank you

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