XPS 13 9370, no longer booting up

Dell does not do data recovery.  There are plenty of options for that.  For $30 or so you can buy an NVMe to USB enclosure and simply mount the drive into it, attach it to a working Linux system and copy your data files.

If you can't or won't do that, there are plenty of places that do data recovery.  It should be inexpensive and straightforward as long as the drive is undamaged.  If it is damaged however, note that SSD data recovery can easily reach into the thousands of dollars to have done.

@ejn63​ thank you. I am aware of the option NVMe to USB enclosure but have never done this — what I am worried about is that the SSD got damaged. 
Does Dell have walk in technical support to assess the situation in Asia? It seems there is none in Hong Kong … what about Shenzhen. I would be tremendously grateful if you could provide some reliable third party vendors that I can contact; additional support list of Dell experts to asses the situation. 

As I wrote, Dell is not in the data recovery business, so they're not going to evaluate your system.  It sounds like this system is at least several years old, and Dell -- like just about every other manufacturer -- generally won't have parts to repair a system more than 4-5 years old.

There are data recovery services Dell recommends -- Gillware is one of them.  There are plenty of others that may have a more extensive presence outside the US, where Gillware is based.  You'll need to evaluate the value of the data against the cost of recovery, but Gillware and others will evaluate the drive and generate a firm estimate for recovery before they begin the process.  As I mentioned, though -- data recovery from SSD is labor intensive and depending on what is involved, will easily cost multiple thousands of dollars to have done.

@ejn63​ I made some progress and with some trial and error detected what the real culprit is —- battery!!! While I don’t have the screw drivers to remove the battery I was able to unplug the battery and directly  power via AC adapter. 
The problem is not solved completely. Recall this is a pre installed Linux machine. So now it doesn’t boot correctly into the Ubuntu. 

i went into the boot menu via F2, and realized the resetting happened on clock … so I think that under system configuration: sata operation was switched too.  At present there are three choices: disabled, ahci and Raid On. And the clicked on says Raid On. Is it possible that mine was set to AHCI previously? I tried to click on this but get a severe warning message …. “Attention changing this setting may prevent your operating system from booting or require reinstall”. 
since I cannot afford to have a reinstall … I must ask whether this is an option i can try out.

@EG.Dell​ let me answer my own question. Yes I resolved my own problem and probably that of others in the future. 
Changing raid on to ahci in the bios setting resolved the issue. I am able to finally boot back into my system. The issue remains what happens once I unplug the AC adapter again since battery remains unplugged. Sigh. Severely disappointed by the degree of support that Dell offers customers who have spent more than 10k usd over the year. Absolutely grotesque is the inherent battery issue with the XPS series.

@Chino de Oro​  see my follow up post and on going problems while battery replacement. 

are u saying that the cmos battery also needs replacement ?  Coz firm ware bios setting would not simply be reset if u replace the main battery .. is this all symptomatic of cmos battery failure ?