best travel option from chongqing to leshan and mt.emei. train from emei to xian?

You need to take a bullet train from Chongqing to Chengdu East first, which takes about 2 hours.

Then you can take a bullet train to Leshan, which takes about 1 h. After that, take Bus 605 to the Buddha.

Then back to Leshan Station and take another bullet train to Emeishan, which takes about 15 minutes. Then take Bus Emeishan 12 to Baoguosi Temple, which is in the Mount. Emei.

As for trains to Xian, I didn’t find any bullet train available from the four places. You may take a bullet train to Chengdu South, which takes about 1h 20 minutes.
Then take a taxi to the airport and take a flight to Xian, which leaves at 14;10 and 18:50, taking about 1h 30 minutes.