why is my s3 neo doing this?

[AC Question]

so for some unknown reason my phone suddenly started doing some glitchy stuff

for example
when i press the home or the power button to go to the lock screen it takes about 30 seconds to open

when i press the volume buttons they glitch out and dont appear for 10-20 seconds and dont disappear when they appear

and when i open the lock screen it glitches alot and then i get the message
"sorry process system has stopped responding do you want to close it ?"
or "sorry touch wiz home has stopped responding do you want to close it?"

even my music player doesnt open any type of audio file
not even mp3 it says music player doesnt support this type of file
same with google play music

android kit kat 4.4.2

have tried flashing via odin like many times before i know how the steps go thats cause i have flashed many custom roms in my old s3 mini

but i decided to switch to s3 galaxy neo and it was working fine for a month or so
until this thing happened, when i try to flash it says aboot secure check failed

i have rooted the phone via king root cause i was lazy to root via pc but i have unrooted it

also i used smart switch to re flash my stock rom but no luck
i have cleared cache and factory reset 2 times now but no luck there either

and to mention i did do the factory reset via recovery but not via settings

also this happened right after i plugged in my headphones i noticed it glitching out and unplugged them but no difference
help please ?

thanks

 

[halp me]

also i failed to mention i have absolutely no sound at all

everything that is sound related
calls,the volume , youtube, s voice and etc are glitchy and laggy and barely work

 

[halp me]

and why has no one replied yet :/

 

[halp me]

Update:
I flashed it again and i cleared cache (if i remembered how to spell it correctly)

And i no longer get the process system has stopped and the touch wiz thing either

But i am still having sound issues
I think i found the problem tho

Whenever i try to use a program that requires the mic it says that another program is using it and i dont know which one is

Also phone vibrates randomly now
And when pressing the silent , vibrate and loud setting it lags the device when going to loud