Travelling Tips! (Kunming-Shanghai-Beijing)

I will go to Kunming, Shanghai & Beijing. My flight date is 9th August 2017 to Kunming at 19:00. On 11th August (Morning), I've plan to go Shanghai by Bullet Train. On 12th August (Morning), I'll go to Beijing with Bullet Train also. On 14th August, I'll back to Kunming from Beijing by Bullet Train. On 15 August, I've flight for Dhaka at 13.00. So my questions are-
1) What places should I cover in Kunming & Beijing in these days? Great Wall is must to see!
2) Can I get Bullet train tickets on travelling date? If no, what should I do?
3) Which part/section should I visit for Great Wall view?
4) Which places should I stay in Kunming & Beijing? (Considering Nightlife, Shopping, Entertainment)
5) Is I-phone & electronic items are cheaper in China? In which places can I get the cheapest with quality?