This derailleur is down pull only so won't be compatible with top tube routing

Braze on means that there is a mount already brazed onto the frame. The Derailleur bolts onto this mounting. The majority of manufacturers use band on fittings which consist of a band (clamp) that encircles the tube. The advantage is that there is more height adjustment (if you were switching from normal to compact chainset on a road frame for instance) but the disadvantage is that they don't always fit frames with non circular tubes...rarely a problem.

You can use 10 speed items with 9 speed setups. You may need to be careful with your setup of the front mech, also make sure that you order double or triple depending on the amount of rings that you have on your chainset.

Unfortunately we do not stock Orbea so I can't tell you the size you require. I would recommend contacting Orbea or measuring your bikes outside diameter of the seat tube.