Yes Yves,
Upgrade is technically possible from any of the versions, but it was not tested in internal databases hence SAP doesn't recommend/support these type of upgrades. Entire responsibility of issues/bugs should be owned by customer only.
We strongly recommend a minimum release 10.2.0.4 for the following reasons:
a) All SAP internal database upgrade tests have been performed with
release 10.2.0.4. This upgrade path has been very well tested and
is documented in the SAP Database Upgrade Guide for Oracle Release
11.2.
Seems my words are misleading! I just mentioned not possible because it is not recommended.
Regards,
Nick Loy