Thirupathi and Balaji are intriguing.

They are beyond reason.

Before I proceed to narrate the relevant subject,let me add my personal experience.

When I was around thirteen or fourteen years old,I had burning sensation in my stomach and Doctors were divided in their opinion, whether it was Hyperacidity or Ulcer.

Ulcer was ruled out.

Antacids were prescribed.

Along with it I was taking Palm Juice, பதநீர்,in early mornings for over two years.

The disease got worse to such an extent, I recall lying face down with stomach pressed down to Cement floor thinking it would cool my stomach.

One day,my father said he would no longer consult doctors or offer any medicines.

Instead he would leave it to Thirupathi Balaji to cure it and vowed that he would perform my Upanayana at Thirupathi.

Within an hour I was relieved of the burning sensation.

Never has stomach related issues from then onwards.

Of course,my Upanayana was performed at Tirupathi..

I had also written on why no one should set time to Him.

Now to the issue on hand.

It is said that no one can see the back side of Balaji.

At those who have attempted had lost their eyesight.

The information is credible as it comes from a descendant of Thirupathi Archakas who have been serving Him since 19th Century.

Excerpt.

‘

The back side of the Venkateshwara deity has the incarnation of badrakali the Kali Swaroopa inside Vishnu that slayed Hiranyayaksha( as Govinda means a name of Varaha the wild boar form that slayed the demon) and the height of the deity is made up the height of Lord Krishna in Dwapara Yuga. There are credible stories of few people losing their eyesight when they tried acting smart by trying to worship from behind. The moola murthy Stone was cut from Sila thoranam a bunch of rocks approximately 12 crore (120 million yrs old) years old the remains you can see in Tirupati itself in the fenced park outside the bus stand.

How am I qualified and informative enough to say this, my maternal grandfathers grandfather and his predesscors were the chief priests of Tripathi during the 19th century and before they were touching the deity and performing Brahma karma and incidentally the clan who got first respect and was holding the parivattam of the Temple devastana bestowed by the kings and later by the Brits as per the lineage’

Source.

Sri. Vijaya Raghavan at Quora.

https://www.quora.com/Why-is-it-said-that-no-one-can-touch-the-back-of-the-idol-of-Shri-Balaji-of-Tirupati-Balaji-Temple/answer/Vijay-aRaghavan?ch=10&share=a6d6db4e&srid=pNfl