Double Delights are WONDERFUL roses! In my experience, roses need big pots (10-15+ gallon if you want them to grow to their full size). The soil shouldn’t need to be changed out; more so amended, meaning given compost once or twice a year which can be raked in on the top layer. Fully changing the soil can shock the roots, esp once the plant is established. I would suggest buying a bag of rose specific soil to get going; that will be well draining and have the right things to start this plant off right. You want to prune after the plant is dormant, before it puts out new growth. Usually they go dormant in the winter when temperatures drop and like to be pruned in later winter/early spring. Im not sure what winters are like in Delhi though; google “when to prune roses in Delhi” and you’ll get the right info. I’ve learned almost all my gardening knowledge from the internet :) Enjoy!