I was born in a city called "X", but now i’ve moved 5 years ago to "Y". So in "Y" I pray 4 rakaat normally but they told me in "X" I need to pray 2 rakaats now if i stay there less than 10 days. I don't own or house or anything in "X".

If you left the "X" and you are not considering that place as your hometown then your namaz will be Qasr (means you have to pray zohr,Asr and Isha 2 Rakat)