Update to 4.3 or higer and issue with phone turning off?

Question

Hi, I have a couple of questions regarding my Xperia C which none of your Support team were able to answer after several emails sent through your "Contact Us" page:
1. Will Xperia C be upgraded to 4. 3 or higher? If yes, then when? If not, then why?
2. My phone most of the times shuts down and is unable to turn it on without having to do a hard reset of the unit while I play songs using the Walkman app through the speakers of the phone. The back panel heats up as well whenever this happens.
3. Some of the files stored in my SD card went missing and would only reappear if and when I restart my phone. Then after a couple of hours (8-9 the most or earlier than that if I use some of the device' apps and internet) some of the files (recently downloaded pics/songs and recently made playlists in the Walkman, Albums and Movies apps) would disappear again. Already did a phone repair via PC Companion, erased SD Card files via phone and transferred them all back in after the phone repair but it stiĺ replicates the issue. Thought it was my SD card who is at fault here but when I used the same SD card on my brother's Xperia Z, the issue did not manifest after 2 days of monitoring.
Already went to the Xperia Shop to have it che ked but they only resorted to doing the same system upgrade/repair that I did. They also suggested to have my phone checked at the main tech hub but it would take 2-3 weeks to diagnose and there is no assurance that they can ißue a service unit while my Xperia C Dual is being repaired. I can't afford to lose a phone even for a day as both numbers that I am using on my Xperia phones are being used for my 2 businesses that transacts 18 hours a day.
Hope any of you moderators could answer the above queries without having to just redirect said concerns to your Contact Us page.
Please do answer the above queries, even for just points 1 and 2 if you really have no idea how to solve point 3.
Your prompt response regarding the said concerns will be highly appreciated.

Answer 1

Thank you so much for the quick response regarding Xperia C updates, Thommo and Rickard.
However, is there a way that you guys can send a screenshot of the said site in this thread when you access the link? Reason being whenever I access the said link, whether it be thru my Xperia phone or my laptop and PC, the page/site only gives out info on how to update the Xperia C phoneand info about the latest Android Version, Build Number and RRelease Date of the said version. No info whatsoever that it is the last or final update that Xperia C will be receiving. Not sure though if it is because of the clause in the said page that "updates depends on the country to where you purchased/use your unit" that the info differ as well. I am currently located in Manila Philippines though when accessing the link.
Rickard, to answer your question: yes, I already tried using the same SD card on another Xperia device and it didn't replicate the issues I am having with my Xperia C. And just about a few hours ago, I used a different SD card for my Xperia C phone and the same issue happens. Whether I set the default storage to PHONE, SD CARD, or LET THE SYSTEM DECIDE, the same issue of recent files being erased happens.
One more thing though which I think is worth noting, per my observation, this issue happens whenever the CACHED DATA of the DEVICE MEMORY reaches 65-70 MB something which is hard to monitor especially if you are using your phone for video calls/VOIP and net related activities especially on my part who is very busy having to work 18 hours a day to keep up with the demands of handling my two businesses of different nature.
Further inputs will be greatly appreciated guys. Thanks in advance.