There have been some great posts recently on how to deploy a CRM2011/CRM2013 solution to CRM2015.
1.Deepesh Somani -> https://dynamicsofdynamicscrm.wordpress.com/2014/12/05/issue-resolutionsolution-compatibility-crm-2013-to-crm-2015/
2. Andre Margono -> https://andz88.wordpress.com/2015/03/02/unsupported-customisation-importing-crm-2011-managed-solution-to-crm-2015/
2. Andre Margono -> https://andz88.wordpress.com/2015/03/02/unsupported-customisation-importing-crm-2011-managed-solution-to-crm-2015/
I had recently to deploy one, the other way around: from CRMOnline to a CRM2013 instance. In my case the solution contained only html, png and Javascript webresources.
The entity dependencies for the solution, were already present in the CRM2013 organisation. The CRM2013 organisation was on SP1 UR1 (6.1.1). Refer to https://support.microsoft.com/en-us/kb/2917899 if you are on a higher/lower rollup and modify the version number appropriately.In order to import the CRMOnline solution I had to
1. Extract the solution zip file
2. Change the first line of the solution.xml
from
<ImportExportXml version="7.0.0000.5026" SolutionPackageVersion="7.0" languagecode="1033" generatedBy="CrmLive" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
to
<ImportExportXml version="6.1.0001.0132" SolutionPackageVersion="6.1" languagecode="1033" generatedBy="CrmLive" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
3.Delete <IsEnabledForMobileClient>0</IsEnabledForMobileClient> from every single webresource node in customizations.xml
4. Rezip the files
After performing these steps, I was able to import the solution into the CRM2013 environment. As with the other two posts, this is an unsupported method, so use it at your own risk.
Dreaming in CRM & Power Platform 