Help If I put an Android Mod (4.1+ or 4.2+) on my phone, will it slow the speed?

[easybullet3]

Will putting a mod of the latest version of android on my phone cause my phone to slow down or have memory issues?

i am currently using android 4.0.3 on my Galaxy S2 (international version - unlocked).

ALSO:
is 4.0.3 the highest version of android that can be used on my phone??
When I click on UPDATE SOFTWARE, it says there are no updates!!
I'm sure I was told (when I bought the phone) that it can update to android 4.1

please please someone answer

 

[ironass]

Will putting a mod of the latest version of android on my phone cause my phone to slow down or have memory issues?

i am currently using android 4.0.3 on my Galaxy S2 (international version - unlocked).

If you are upgrading to Jelly Bean, it should be better.

ALSO:
is 4.0.3 the highest version of android that can be used on my phone??
When I click on UPDATE SOFTWARE, it says there are no updates!!
I'm sure I was told (when I bought the phone) that it can update to android 4.1

please please someone answer

See posts #1,#2 and #3 of the Jelly Bean update - Dummies Guide to see if there is a Jelly Bean update for your phone and for reasons you may not be able to update it using Kies and what you can do to update it yourself.

Grab a coffee and carefully and thoroughly, read through those posts as they will answer all your questions.