Assalamualaykum, I moved from my home city to a new city because I got a job. I am not sure if I will ever move back to my home city. For the holidays I went back to my home city to visit my family. Can I combine and shorten prayer? Does it matter if I am staying for more than 15 days? JazakAllah

Since u moved and this is no longer your place of permanent residencey then yes u can shorten the salah, but don't combine unless there is a need or you are on the journey itslef. As for 15 days the correcr answer is that there is no evidence for a time limit as sh Al Islam Ibn Taymiyyah has mentioned.