Hello Ramso,
1. Could you please let us know the Target version ?? What do you mean by ECC EHP 7.0 ??
EHP7 is not released...below given versions are available.
EHP6 for SAP ERP 6.0
EHP5 for SAP ERP 6.0
EHP4 for SAP ERP 6.0
EHP3 for SAP ERP 6.0
EHP2 for SAP ERP 6.0
EHP1 for SAP ERP 6.0
2. What is the add-on name??
General steps will be to check if the add-on is compatible with the target system version. If not then you will have to upgrade the add-on to compatible release. If it is compatible then we have 2 options
a) Vendor key (old method used...now used for very few add-ons)
b) ACPs (new method...sap provides the ACP for the add-on)
Best way is to calculate these things during the MOPZ (stack.xml file generation).
I hope it helps.
Regards,
Gaurav