1) Can I use Inquiry Pro on more than one PC with a single license key? (I am the only user on all my 3 PC's)
2) Can I merge the saved data from different PC's (if the answer to #1 is "yes"). If yes, how can I merge saved data? Thanks
1) Yes, you can. A license key is for user, not for PC.
2) You can use Google Drive or Sky Drive. Any Inquiry collection is a set of small files and it well synchronized with this tools. Or you can use backup\restore tools in Inquiry.