Hi Tommy,
Appreciate for your prompt response.
Yes true, this R2CU7.axmodelstore and Model DB I have exported from my Production Server (R2 CU7). Yes true both are same one is from SSMS and other is a file using AXUtil. This i have picked from my PRODCUTION Sever and I would be using the file "R2CU7.axmodelstore".
Ok. So I guess I am clear now. Kindly find the detailed steps below:
Note-1: (Below some points are redundant between point #1 to #5. I am explaining the things for normal scenario)
(For Below point I have referred to this blog - http://www.msdynamicsax.info/)
Step-1. On my new fresh Test Server, I will uninstall the R3 CU11 completely.
Step-2. On my this test server, I will first installed the COPY of my PROD i.e. R2 CU7 with the last model_DB and Business Data.
(Make it Replica of Production)
Step-3. Now I will perform AOT Compile, Full CIL + Db Synch. in order to make it error free if any.
Step-4. I will take the backup of modelstore and business data of R2 CU7.
Step-5. Now i will uninstall all my R2 CU7 components from my Test Server.
Note: So now in SSMS\Databases, we have MicrosoftDynamicsAX , MicrosoftDynamicsAX_model , MicrosoftDynamicsAXBaseline ( of R2 CU7 )
Step-6. Start the AX 2012 R3 installation setup on a new environment as below,
Step-7. Select only the databases component.
Step-8. Select configure existing databases (Which is of R2 CU7 inside SSMS)
Step-9. In this step, Assign the R2 database (
MicrosoftDynamicsAX of R2 CU7) and make sure that the
Baseline database name field is left blank during this procedure.
Step-10. On the Select additional models page, select the Foundation model, Foundation Upgrade model, and any other models that you require for your deployment. Select the Foundation Labels model only if you are using country/region-specific features.
After this step, the system creates a new baseline database which contains upgraded AX 2012 R3 models in the SYS, GLS, FPK, and SLN layers and Non-upgraded customer models in the ISV, VAR, CUS, and USR layers.
Step-11. Now install all other required AX components.
Step-12. Now, assign the database and upgraded baseline database in this step.
QUERY-1: Are these 2 DBs in below snapshot, MicrosoftDynamicsAX116 & MicrosoftDynamicsAX116_UpgradeR3Baseline that we would be selecting in this step generated after Step-10 above ?

Step-13. Once, the installation is completed then compile the whole application using the command “axbuild xppcompileall” from the command prompt. This compiled the whole application for me in just 30 to 40 minutes.

Step-14. Now restart AOS and proceed with the code upgrade & data upgrade checklists. Follow the code upgrade document on the complete details.
There is one QUERY-1 and NOTE-1 above in RED, if you can confirm on both.
Rest, can you please confirm on my understanding if I have understood things properly.
Thank a lot in advance for the same.
Sincerely,
Muneeb