I guess your issue is with interpreting DB2 version numbers. The structure is like this: <major>.<minor>.<fix-pak>. So the 3rd portion is the fix pak number already. Hence, 8.1.14 is DB2 V8.1 with FixPak 14. If you had V8.1 FP12, you would have seen V8.1.12. Thus, the statement you had version V8.1.14 FixPak 12 is a contradiction in itself.
Also, my question still holds: why did you want to deinstall DB2 V8.2 and install it again? That really doesn't make any sense to me. You already had V8.2 installed because V8.1.7 <i>is the same</i> as V8.2. Since you had FixPak 12 or 14 already installed, which includes the functionality of FixPak 7, you had the V8.2 plus some fixes. From that perspective, you spent effort on a task that was not needed at all.