Bing de-indexed our site from search. Site Ranking Good in Google and All Content are genuine.

Already posted in Bing Webmaster Forum  and send multiple emails for last 2 months. No response over email and no fruitful response in forum. Our customer unable to find us in bing.com as bing de-indexed our website even bing search suggesting our brandname "5bestincity" while typing but no result once user clicked it. 

Issues in short:

Our Site currently not showing in bing search. Though site crawled regularly and image search showing result.
But regular search have no result even if we search for "site:5bestincity.com"
Our website was ranked extremely well in Bing when it was indexed and similarly we are currently ranking extremely good in Google too.
All Our content and image manually collected and organized and written by us and we regularly talk with business owner for updated information.
We are really surprised why bing gave us penalty.
We have two other domain top5incity.com and best5incity.com to prevent our brand misuse and we had started to develop our website for internal purpose using that two domain and we strictly mentioned through robots.txt not to crawl.
despite that bing crawled and indexed those two website and it was ranked also good in bing.
We are forced to remove all result manually from bing as soon we noticed duplicate site result.
We never asked bing to crawl and index or anything to do that duplicate domain. and it completely ignore robots.txt.
But suddenly in november end bing entirely removed our main website 5bestincity.com from its search.
Bing de-indexed our site from search. Site Ranking Good in Google and All Content are genuine.
if you go through our screenshot you may noticed development site ranks 2 despite no index declaration.

Please bing clarify what we did wrong and help us to be in your search result.

If we violates and used any technique which is against your policy , guide us we will definitely take action.
We have send almost 6 email starting from November end. But no reply still now.

Its urgent as many client and business owner complaining that they are unable to find our website in bing.com and it jeopardize our effort also Bing search suggestion providing our brandname which means many users searching with our brand name , please help us to resolve it immediately.

I am attaching few screenshot related to webmaster portal to understand better. Url inspection showing us alert that we may have violated webmaster guidelines, but we have read and tried to figure out any rules which Bing may find as violation but really unable to do. 

We need help to resolve it immediately as it may lead bad user experience as well our customer complaining daily about our website absence in bing.