I have Nexus 7 2012 version unrooted and it has Android KitKat 4.2.2 version. The problem is that my tablet has become very slow and sometimes behaves strangely. Another problem I am facing is that sometimes I am unable to access Google Play store. When I try to open it I see the message "Redeem your code", "Gift Card & Promotional Code". Sometimes the play store opens accidently but soon it closes and the above mentioned message appears. Also from other forums some people advised the following but no one gave me any links to the guides from where I could understand how to do what they advise. They advised 1- To clear cache and data. and 2- Boot to recovery, 3- Clear Dalvik cache, Restart. I could only search the below guides:

For Cache Partition Wipe I found:
[GUIDE] Nexus 7 (2012 & 2013) Cache Partition Wipe - Android Forums at AndroidCentral.com

For boot to recovery I found:

How to boot into Recovery Mode Nexus 7 | Rob Schmuecker

But I can't find any guide to clear Dalvik cache and clear data. I asked about that from them but no one replied. Could you be kind enough to guide me what to do and what not and provide me some information about this?