This is a very open-ended question. But, I shall give you a scenario here. You have yet to mention whether you want to travel in Economy or Business. That is a major decision point.
If you want to book a non-stop flight from Bombay to Hong Kong using miles/points in economy class, your only option is Cathay Pacific, which is a One World airline. To book you should go through Qatar Airways, the only one-world partner airline available with Axis points. You need to transfer your Avios points to British Airways from QR (both use the same currency), as QR charges 35,000 Avios for economy and 70,000 for business class. Transferring the Avios from QR to BA allows you to book the same flight for 13,000 miles and roughly $140 in taxes. But the same flight has a cash fare of Rs 25892 in economy (one-way) when booked directly through CX- one-way international tickets may be expensive while paying cash, so if paying cash, book roundtrip.
If you are okay with having a stopover, you can fly on Singapore airlines, which has a cash fare of Rs 29,037 for a BOM-HKG-BOM roundtrip.
P.S: The flight costs quoted were checked for random dates of June 13 to June 17.
It's important to consider your constraints and preferences when deciding to whether to pay with miles or cash and whether to travel in economy or business class. Also for your last question, since you have a Magnus card, you can transfer ER points to partners at a ratio of 5:4.
