Pay protection from higher to lower post

Sir, I would like to get some information on the case that I had joined as an LDC on 01 Sep 2000 in the AFHQ Cadre in the basic pay 3050-4590 through SSC clerical grade exam. On 24 dec 2007 I was promoted to the grade of UDC ( Basic pay 4000-6000) it was revised as [deleted] with GP 2400 in 6th CPC. Again on 24 hum 2015 i was promoted to the post of Assistant now ASO in Pay of ([deleted]) with GP 4600. I had applied for SSC combined graduate level exam 2013 through proper channel and was qualified for the post of Auditor . As such i have joined as Auditor in the O/o Aaccountant general on 01 April 2016 after accepatnce of technical resignation by ex employer . As i have joined as an Auditor basic pay 29200/- , but as per Last pay certificate my basic was Rs 10110 with grade pay 4600( as per 6th cpc). My lien granted in the post of UDC. Plz provide me this information. 1. What will be my first basic in the new post ,how my fixation will be done as per 7th CPC. 2. Which Fundamental rule applicable in protection of pay in the above mentioned case. Thanking you